diff --git a/test/accessibility.spec.js b/test/accessibility.spec.ts
similarity index 99%
rename from test/accessibility.spec.js
rename to test/accessibility.spec.ts
index 858359aa00..6e8a3ff316 100644
--- a/test/accessibility.spec.js
+++ b/test/accessibility.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
diff --git a/test/assets/shadow.html b/test/assets/shadow.html
index 7242e673b5..d1fd331eb2 100644
--- a/test/assets/shadow.html
+++ b/test/assets/shadow.html
@@ -1,7 +1,7 @@
 <script>
 
 let h1 = null;
-let button = null;
+window.button = null;
 let clicked = false;
 
 window.addEventListener('DOMContentLoaded', () => {
diff --git a/test/browsercontext-csp.spec.ts b/test/browsercontext-csp.spec.ts
index b47d322017..ede92827e2 100644
--- a/test/browsercontext-csp.spec.ts
+++ b/test/browsercontext-csp.spec.ts
@@ -24,8 +24,8 @@ it('should bypass CSP meta tag', async({browser, server}) => {
     const context = await browser.newContext();
     const page = await context.newPage();
     await page.goto(server.PREFIX + '/csp.html');
-    await page.addScriptTag({content: 'window.__injected = 42;'}).catch(e => void e);
-    expect(await page.evaluate('window.__injected')).toBe(undefined);
+    await page.addScriptTag({content: 'window["__injected"] = 42;'}).catch(e => void e);
+    expect(await page.evaluate('window["__injected"]')).toBe(undefined);
     await context.close();
   }
 
@@ -34,8 +34,8 @@ it('should bypass CSP meta tag', async({browser, server}) => {
     const context = await browser.newContext({ bypassCSP: true });
     const page = await context.newPage();
     await page.goto(server.PREFIX + '/csp.html');
-    await page.addScriptTag({content: 'window.__injected = 42;'});
-    expect(await page.evaluate('window.__injected')).toBe(42);
+    await page.addScriptTag({content: 'window["__injected"] = 42;'});
+    expect(await page.evaluate('window["__injected"]')).toBe(42);
     await context.close();
   }
 });
@@ -48,8 +48,8 @@ it('should bypass CSP header', async({browser, server}) => {
     const context = await browser.newContext();
     const page = await context.newPage();
     await page.goto(server.EMPTY_PAGE);
-    await page.addScriptTag({content: 'window.__injected = 42;'}).catch(e => void e);
-    expect(await page.evaluate('window.__injected')).toBe(undefined);
+    await page.addScriptTag({content: 'window["__injected"] = 42;'}).catch(e => void e);
+    expect(await page.evaluate('window["__injected"]')).toBe(undefined);
     await context.close();
   }
 
@@ -58,8 +58,8 @@ it('should bypass CSP header', async({browser, server}) => {
     const context = await browser.newContext({ bypassCSP: true });
     const page = await context.newPage();
     await page.goto(server.EMPTY_PAGE);
-    await page.addScriptTag({content: 'window.__injected = 42;'});
-    expect(await page.evaluate('window.__injected')).toBe(42);
+    await page.addScriptTag({content: 'window["__injected"] = 42;'});
+    expect(await page.evaluate('window["__injected"]')).toBe(42);
     await context.close();
   }
 });
@@ -68,12 +68,12 @@ it('should bypass after cross-process navigation', async({browser, server}) => {
   const context = await browser.newContext({ bypassCSP: true });
   const page = await context.newPage();
   await page.goto(server.PREFIX + '/csp.html');
-  await page.addScriptTag({content: 'window.__injected = 42;'});
-  expect(await page.evaluate('window.__injected')).toBe(42);
+  await page.addScriptTag({content: 'window["__injected"] = 42;'});
+  expect(await page.evaluate('window["__injected"]')).toBe(42);
 
   await page.goto(server.CROSS_PROCESS_PREFIX + '/csp.html');
-  await page.addScriptTag({content: 'window.__injected = 42;'});
-  expect(await page.evaluate('window.__injected')).toBe(42);
+  await page.addScriptTag({content: 'window["__injected"] = 42;'});
+  expect(await page.evaluate('window["__injected"]')).toBe(42);
   await context.close();
 });
 
@@ -84,8 +84,8 @@ it('should bypass CSP in iframes as well', async({browser, server}) => {
     const page = await context.newPage();
     await page.goto(server.EMPTY_PAGE);
     const frame = await utils.attachFrame(page, 'frame1', server.PREFIX + '/csp.html');
-    await frame.addScriptTag({content: 'window.__injected = 42;'}).catch(e => void e);
-    expect(await frame.evaluate('window.__injected')).toBe(undefined);
+    await frame.addScriptTag({content: 'window["__injected"] = 42;'}).catch(e => void e);
+    expect(await frame.evaluate('window["__injected"]')).toBe(undefined);
     await context.close();
   }
 
@@ -95,8 +95,8 @@ it('should bypass CSP in iframes as well', async({browser, server}) => {
     const page = await context.newPage();
     await page.goto(server.EMPTY_PAGE);
     const frame = await utils.attachFrame(page, 'frame1', server.PREFIX + '/csp.html');
-    await frame.addScriptTag({content: 'window.__injected = 42;'}).catch(e => void e);
-    expect(await frame.evaluate('window.__injected')).toBe(42);
+    await frame.addScriptTag({content: 'window["__injected"] = 42;'}).catch(e => void e);
+    expect(await frame.evaluate('window["__injected"]')).toBe(42);
     await context.close();
   }
 });
diff --git a/test/browsercontext-expose-function.spec.ts b/test/browsercontext-expose-function.spec.ts
index 373f0858b6..3587974a09 100644
--- a/test/browsercontext-expose-function.spec.ts
+++ b/test/browsercontext-expose-function.spec.ts
@@ -72,9 +72,9 @@ it('should be callable from-inside addInitScript', async({browser, server}) => {
   await context.exposeFunction('woof', function(arg) {
     args.push(arg);
   });
-  await context.addInitScript('woof("context")');
+  await context.addInitScript('window["woof"]("context")');
   const page = await context.newPage();
-  await page.addInitScript('woof("page")');
+  await page.addInitScript('window["woof"]("page")');
   args = [];
   await page.reload();
   expect(args).toEqual(['context', 'page']);
diff --git a/test/browsercontext-locale.spec.ts b/test/browsercontext-locale.spec.ts
index cd71605cbc..c51421df55 100644
--- a/test/browsercontext-locale.spec.ts
+++ b/test/browsercontext-locale.spec.ts
@@ -83,7 +83,7 @@ it('should format number in popups', async({browser, server}) => {
     page.evaluate(url => window.open(url), server.PREFIX + '/formatted-number.html'),
   ]);
   await popup.waitForLoadState('domcontentloaded');
-  const result = await popup.evaluate('window.result');
+  const result = await popup.evaluate('window["result"]');
   expect(result).toBe('1 000 000,5');
   await context.close();
 });
diff --git a/test/browsertype-launch-server.spec.js b/test/browsertype-launch-server.spec.ts
similarity index 94%
rename from test/browsertype-launch-server.spec.js
rename to test/browsertype-launch-server.spec.ts
index 067c8a1202..e5edf6cd31 100644
--- a/test/browsertype-launch-server.spec.js
+++ b/test/browsertype-launch-server.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const fs = require('fs');
-const utils = require('./utils');
+import path from 'path';
+import fs from 'fs';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should work', async({browserType, defaultBrowserOptions, toImpl}) => {
@@ -71,11 +71,11 @@ it('should return child_process instance', async ({browserType, defaultBrowserOp
 it('should fire close event', async ({browserType, defaultBrowserOptions}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const [result] = await Promise.all([
-    new Promise(f => browserServer.on('close', (exitCode, signal) => f({ exitCode, signal }))),
+    new Promise(f => (browserServer as any).on('close', (exitCode, signal) => f({ exitCode, signal }))),
     browserServer.close(),
   ]);
-  expect(result.exitCode).toBe(0);
-  expect(result.signal).toBe(null);
+  expect(result['exitCode']).toBe(0);
+  expect(result['signal']).toBe(null);
 });
 
 it('should reject navigation when browser closes', async({browserType, defaultBrowserOptions, server, toImpl}) => {
@@ -117,7 +117,7 @@ it('should throw if used after disconnect', async({browserType, defaultBrowserOp
   const page = await remote.newPage();
   await remote.close();
   const error = await page.evaluate('1 + 1').catch(e => e);
-  expect(error.message).toContain('has been closed');
+  expect((error as Error).message).toContain('has been closed');
   if (toImpl)
     await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
@@ -129,7 +129,7 @@ it('should emit close events on pages and contexts', async({browserType, default
   const context = await remote.newContext();
   const page = await context.newPage();
   let pageClosed = false;
-  page.on('close', e => pageClosed = true);
+  page.on('close', () => pageClosed = true);
   await Promise.all([
     new Promise(f => context.on('close', f)),
     browserServer.close()
diff --git a/test/channels.spec.ts b/test/channels.spec.ts
index e3607786ae..68dcf25320 100644
--- a/test/channels.spec.ts
+++ b/test/channels.spec.ts
@@ -17,7 +17,7 @@
 import './base.fixture';
 
 import utils from './utils';
-import { ChromiumBrowser } from '../types/types';
+import { ChromiumBrowser } from '..';
 const { FFOX, CHROMIUM, WEBKIT, WIN, CHANNEL } = testOptions;
 
 it.skip(!CHANNEL)('should work', async({browser}) => {
diff --git a/test/chromium/chromium.spec.js b/test/chromium/chromium.spec.ts
similarity index 84%
rename from test/chromium/chromium.spec.js
rename to test/chromium/chromium.spec.ts
index ce796bd004..d98892c6be 100644
--- a/test/chromium/chromium.spec.js
+++ b/test/chromium/chromium.spec.ts
@@ -13,13 +13,14 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('../base.fixture');
+import '../base.fixture';
+import { ChromiumBrowserContext } from '../..';
 
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL} = testOptions;
 
 it.skip(!CHROMIUM)('should create a worker from a service worker', async({page, server, context}) => {
   const [worker] = await Promise.all([
-    context.waitForEvent('serviceworker'),
+    (context as ChromiumBrowserContext).waitForEvent('serviceworker'),
     page.goto(server.PREFIX + '/serviceworkers/empty/sw.html')
   ]);
   expect(await worker.evaluate(() => self.toString())).toBe('[object ServiceWorkerGlobalScope]');
@@ -27,17 +28,17 @@ it.skip(!CHROMIUM)('should create a worker from a service worker', async({page,
 
 it.skip(!CHROMIUM)('serviceWorkers() should return current workers', async({page, server, context}) => {
   const [worker1] = await Promise.all([
-    context.waitForEvent('serviceworker'),
+    (context as ChromiumBrowserContext).waitForEvent('serviceworker'),
     page.goto(server.PREFIX + '/serviceworkers/empty/sw.html')
   ]);
-  let workers = context.serviceWorkers();
+  let workers = (context as ChromiumBrowserContext).serviceWorkers();
   expect(workers.length).toBe(1);
 
   const [worker2] = await Promise.all([
-    context.waitForEvent('serviceworker'),
+    (context as ChromiumBrowserContext).waitForEvent('serviceworker'),
     page.goto(server.CROSS_PROCESS_PREFIX + '/serviceworkers/empty/sw.html')
   ]);
-  workers = context.serviceWorkers();
+  workers = (context as ChromiumBrowserContext).serviceWorkers();
   expect(workers.length).toBe(2);
   expect(workers).toContain(worker1);
   expect(workers).toContain(worker2);
@@ -46,7 +47,7 @@ it.skip(!CHROMIUM)('serviceWorkers() should return current workers', async({page
 it.skip(!CHROMIUM)('should not create a worker from a shared worker', async({page, server, context}) => {
   await page.goto(server.EMPTY_PAGE);
   let serviceWorkerCreated;
-  context.once('serviceworker', () => serviceWorkerCreated = true);
+  (context as ChromiumBrowserContext).once('serviceworker', () => serviceWorkerCreated = true);
   await page.evaluate(() => {
     new SharedWorker('data:text/javascript,console.log("hi")');
   });
@@ -54,7 +55,7 @@ it.skip(!CHROMIUM)('should not create a worker from a shared worker', async({pag
 });
 
 it.skip(!CHROMIUM)('should close service worker together with the context', async({browser, server}) => {
-  const context = await browser.newContext();
+  const context = await browser.newContext() as ChromiumBrowserContext;
   const page = await context.newPage();
   const [worker] = await Promise.all([
     context.waitForEvent('serviceworker'),
diff --git a/test/chromium/launcher.spec.js b/test/chromium/launcher.spec.ts
similarity index 90%
rename from test/chromium/launcher.spec.js
rename to test/chromium/launcher.spec.ts
index d24c069429..568b500e31 100644
--- a/test/chromium/launcher.spec.js
+++ b/test/chromium/launcher.spec.ts
@@ -13,10 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('../base.fixture');
+import '../base.fixture';
 
-const path = require('path');
-const utils = require('../utils');
+import path from 'path';
+import utils from '../utils';
+import { ChromiumBrowser, ChromiumBrowserContext } from '../..';
 const {makeUserDataDir, removeUserDataDir} = utils;
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS} = testOptions;
 
@@ -41,7 +42,7 @@ it.skip(!CHROMIUM || USES_HOOKS || WIN)('should open devtools when "devtools: tr
     if (parsed.method === 'getPreferences')
       devtoolsCallback();
   };
-  const browser = await browserType.launch({...defaultBrowserOptions, headless: false, devtools: true, __testHookForDevTools});
+  const browser = await browserType.launch({...defaultBrowserOptions, headless: false, devtools: true, __testHookForDevTools} as any);
   const context = await browser.newContext();
   await Promise.all([
     devtoolsPromise,
@@ -60,7 +61,7 @@ it.skip(!CHROMIUM)('should return background pages', async({browserType, default
       `--load-extension=${extensionPath}`,
     ],
   };
-  const context = await browserType.launchPersistentContext(userDataDir, extensionOptions);
+  const context = await browserType.launchPersistentContext(userDataDir, extensionOptions) as ChromiumBrowserContext;
   const backgroundPages = context.backgroundPages();
   let backgroundPage = backgroundPages.length
       ? backgroundPages[0]
@@ -74,7 +75,7 @@ it.skip(!CHROMIUM)('should return background pages', async({browserType, default
 
 it.skip(!CHROMIUM)('should not create pages automatically', async ({browserType, defaultBrowserOptions}) => {
   const browser = await browserType.launch(defaultBrowserOptions);
-  const browserSession = await browser.newBrowserCDPSession();
+  const browserSession = await (browser as ChromiumBrowser).newBrowserCDPSession();
   const targets = [];
   browserSession.on('Target.targetCreated', async ({targetInfo}) => {
     if (targetInfo.type !== 'browser')
diff --git a/test/chromium/oopif.spec.ts b/test/chromium/oopif.spec.ts
index d8beeca36f..d2962a9838 100644
--- a/test/chromium/oopif.spec.ts
+++ b/test/chromium/oopif.spec.ts
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import '../base.fixture';
-import { Page, Browser, BrowserContext } from '../../types/types';
+import { Page, Browser, BrowserContext } from '../..';
 
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL} = testOptions;
 
diff --git a/test/chromium/session.spec.js b/test/chromium/session.spec.ts
similarity index 78%
rename from test/chromium/session.spec.js
rename to test/chromium/session.spec.ts
index 4d0dfd5279..83d8613fa6 100644
--- a/test/chromium/session.spec.js
+++ b/test/chromium/session.spec.ts
@@ -13,23 +13,24 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('../base.fixture');
+import '../base.fixture';
+import { ChromiumBrowserContext, ChromiumBrowser } from "../../types/types";
 
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it.skip(!CHROMIUM)('should work', async function({page}) {
-  const client = await page.context().newCDPSession(page);
+  const client = await (page.context() as ChromiumBrowserContext).newCDPSession(page);
 
   await Promise.all([
     client.send('Runtime.enable'),
     client.send('Runtime.evaluate', { expression: 'window.foo = "bar"' })
   ]);
-  const foo = await page.evaluate(() => window.foo);
+  const foo = await page.evaluate(() => window['foo']);
   expect(foo).toBe('bar');
 });
 
 it.skip(!CHROMIUM)('should send events', async function({page, server}) {
-  const client = await page.context().newCDPSession(page);
+  const client = await (page.context() as ChromiumBrowserContext).newCDPSession(page);
   await client.send('Network.enable');
   const events = [];
   client.on('Network.requestWillBeSent', event => events.push(event));
@@ -38,12 +39,12 @@ it.skip(!CHROMIUM)('should send events', async function({page, server}) {
 });
 
 it.skip(!CHROMIUM)('should only accept a page', async function({page}) {
-  const error = await page.context().newCDPSession(page.context()).catch(e => e);
+  const error = await (page.context() as ChromiumBrowserContext).newCDPSession(page.context() as any).catch(e => e);
   expect(error.message).toContain('page: expected Page');
 });
 
 it.skip(!CHROMIUM)('should enable and disable domains independently', async function({page}) {
-  const client = await page.context().newCDPSession(page);
+  const client = await (page.context() as ChromiumBrowserContext).newCDPSession(page);
   await client.send('Runtime.enable');
   await client.send('Debugger.enable');
   // JS coverage enables and then disables Debugger domain.
@@ -61,7 +62,7 @@ it.skip(!CHROMIUM)('should enable and disable domains independently', async func
 });
 
 it.skip(!CHROMIUM)('should be able to detach session', async function({page}) {
-  const client = await page.context().newCDPSession(page);
+  const client = await (page.context() as ChromiumBrowserContext).newCDPSession(page);
   await client.send('Runtime.enable');
   const evalResponse = await client.send('Runtime.evaluate', {expression: '1 + 2', returnByValue: true});
   expect(evalResponse.result.value).toBe(3);
@@ -76,27 +77,27 @@ it.skip(!CHROMIUM)('should be able to detach session', async function({page}) {
 });
 
 it.skip(!CHROMIUM)('should throw nice errors', async function({page}) {
-  const client = await page.context().newCDPSession(page);
+  const client = await (page.context() as ChromiumBrowserContext).newCDPSession(page);
   const error = await theSourceOfTheProblems().catch(error => error);
   expect(error.stack).toContain('theSourceOfTheProblems');
   expect(error.message).toContain('ThisCommand.DoesNotExist');
 
   async function theSourceOfTheProblems() {
-    await client.send('ThisCommand.DoesNotExist');
+    await client.send('ThisCommand.DoesNotExist' as any);
   }
 });
 
 it.skip(!CHROMIUM)('should not break page.close()', async function({browser}) {
   const context = await browser.newContext();
   const page = await context.newPage();
-  const session = await page.context().newCDPSession(page);
+  const session = await (page.context() as ChromiumBrowserContext).newCDPSession(page);
   await session.detach();
   await page.close();
   await context.close();
 });
 
 it.skip(!CHROMIUM)('should detach when page closes', async function({browser}) {
-  const context = await browser.newContext();
+  const context = await browser.newContext() as ChromiumBrowserContext;
   const page = await context.newPage();
   const session = await context.newCDPSession(page);
   await page.close();
@@ -107,7 +108,7 @@ it.skip(!CHROMIUM)('should detach when page closes', async function({browser}) {
 });
 
 it.skip(!CHROMIUM)('should work', async function({browser}) {
-  const session = await browser.newBrowserCDPSession();
+  const session = await (browser as ChromiumBrowser).newBrowserCDPSession();
 
   const version = await session.send('Browser.getVersion');
   expect(version.userAgent).toBeTruthy();
diff --git a/test/defaultbrowsercontext.spec.ts b/test/defaultbrowsercontext.spec.ts
index d4dae50bbd..0bae14cc88 100644
--- a/test/defaultbrowsercontext.spec.ts
+++ b/test/defaultbrowsercontext.spec.ts
@@ -179,7 +179,7 @@ it('should support userAgent option', async ({server, launchPersistent}) => {
 it('should support bypassCSP option', async ({server, launchPersistent}) => {
   const {page, context} = await launchPersistent({bypassCSP: true});
   await page.goto(server.PREFIX + '/csp.html');
-  await page.addScriptTag({content: 'window.__injected = 42;'});
+  await page.addScriptTag({content: 'window["__injected"] = 42;'});
   expect(await page.evaluate('__injected')).toBe(42);
 });
 
diff --git a/test/dialog.spec.js b/test/dialog.spec.ts
similarity index 99%
rename from test/dialog.spec.js
rename to test/dialog.spec.ts
index 6165530c9b..a9a446de88 100644
--- a/test/dialog.spec.js
+++ b/test/dialog.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL} = testOptions;
 
diff --git a/test/dispatchevent.spec.js b/test/dispatchevent.spec.ts
similarity index 79%
rename from test/dispatchevent.spec.js
rename to test/dispatchevent.spec.ts
index 68840b8286..12e7639737 100644
--- a/test/dispatchevent.spec.js
+++ b/test/dispatchevent.spec.ts
@@ -13,23 +13,23 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS} = testOptions;
 
 it('should dispatch click event', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/button.html');
   await page.dispatchEvent('button', 'click');
-  expect(await page.evaluate(() => result)).toBe('Clicked');
+  expect(await page.evaluate(() => window['result'])).toBe('Clicked');
 });
 
 it('should dispatch click event properties', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/button.html');
   await page.dispatchEvent('button', 'click');
-  expect(await page.evaluate(() => bubbles)).toBeTruthy();
-  expect(await page.evaluate(() => cancelable)).toBeTruthy();
-  expect(await page.evaluate(() => composed)).toBeTruthy();
+  expect(await page.evaluate('bubbles')).toBeTruthy();
+  expect(await page.evaluate('cancelable')).toBeTruthy();
+  expect(await page.evaluate('composed')).toBeTruthy();
 });
 
 it('should dispatch click svg', async({page, server}) => {
@@ -39,7 +39,7 @@ it('should dispatch click svg', async({page, server}) => {
     </svg>
   `);
   await page.dispatchEvent('circle', 'click');
-  expect(await page.evaluate(() => window.__CLICKED)).toBe(42);
+  expect(await page.evaluate(() => window['__CLICKED'])).toBe(42);
 });
 
 it('should dispatch click on a span with an inline element inside', async({page, server}) => {
@@ -52,7 +52,7 @@ it('should dispatch click on a span with an inline element inside', async({page,
     <span onclick='javascript:window.CLICKED=42'></span>
   `);
   await page.dispatchEvent('span', 'click');
-  expect(await page.evaluate(() => window.CLICKED)).toBe(42);
+  expect(await page.evaluate(() => window['CLICKED'])).toBe(42);
 });
 
 it('should dispatch click after navigation ', async({page, server}) => {
@@ -60,7 +60,7 @@ it('should dispatch click after navigation ', async({page, server}) => {
   await page.dispatchEvent('button', 'click');
   await page.goto(server.PREFIX + '/input/button.html');
   await page.dispatchEvent('button', 'click');
-  expect(await page.evaluate(() => result)).toBe('Clicked');
+  expect(await page.evaluate(() => window['result'])).toBe('Clicked');
 });
 
 it('should dispatch click after a cross origin navigation ', async({page, server}) => {
@@ -68,7 +68,7 @@ it('should dispatch click after a cross origin navigation ', async({page, server
   await page.dispatchEvent('button', 'click');
   await page.goto(server.CROSS_PROCESS_PREFIX + '/input/button.html');
   await page.dispatchEvent('button', 'click');
-  expect(await page.evaluate(() => result)).toBe('Clicked');
+  expect(await page.evaluate(() => window['result'])).toBe('Clicked');
 });
 
 it('should not fail when element is blocked on hover', async({page, server}) => {
@@ -83,7 +83,7 @@ it('should not fail when element is blocked on hover', async({page, server}) =>
     <div></div>
   </container>`);
   await page.dispatchEvent('button', 'click');
-  expect(await page.evaluate(() => window.clicked)).toBeTruthy();
+  expect(await page.evaluate(() => window['clicked'])).toBeTruthy();
 });
 
 it('should dispatch click when node is added in shadow dom', async({page, server}) => {
@@ -98,11 +98,11 @@ it('should dispatch click when node is added in shadow dom', async({page, server
   await page.evaluate(() => {
     const span = document.createElement('span');
     span.textContent = 'Hello from shadow';
-    span.addEventListener('click', () => window.clicked = true);
+    span.addEventListener('click', () => window['clicked'] = true);
     document.querySelector('div').shadowRoot.appendChild(span);
   });
   await watchdog;
-  expect(await page.evaluate(() => window.clicked)).toBe(true);
+  expect(await page.evaluate(() => window['clicked'])).toBe(true);
 });
 
 it('should be atomic', async({playwright, page}) => {
@@ -114,17 +114,17 @@ it('should be atomic', async({playwright, page}) => {
         Promise.resolve().then(() => result.onclick = "");
       return result;
     },
-    queryAll(root, selector) {
+    queryAll(root: HTMLElement, selector: string) {
       const result = Array.from(root.querySelectorAll(selector));
       for (const e of result)
-        Promise.resolve().then(() => result.onclick = "");
+        Promise.resolve().then(() => (e as HTMLElement).onclick = null);
       return result;
     }
   });
   await utils.registerEngine(playwright, 'dispatchEvent', createDummySelector);
   await page.setContent(`<div onclick="window._clicked=true">Hello</div>`);
   await page.dispatchEvent('dispatchEvent=div', 'click');
-  expect(await page.evaluate(() => window._clicked)).toBe(true);
+  expect(await page.evaluate(() => window['_clicked'])).toBe(true);
 });
 
 it.fail(WEBKIT)('should dispatch drag drop events', async({page, server}) => {
@@ -132,9 +132,11 @@ it.fail(WEBKIT)('should dispatch drag drop events', async({page, server}) => {
   const dataTransfer = await page.evaluateHandle(() => new DataTransfer());
   await page.dispatchEvent('#source', 'dragstart', { dataTransfer });
   await page.dispatchEvent('#target', 'drop', { dataTransfer });
-  expect(await page.evaluate(() => {
+  const source = await page.$('#source');
+  const target = await page.$('#target');
+  expect(await page.evaluate(({source, target}) => {
     return source.parentElement === target;
-  })).toBeTruthy();
+  }, {source, target})).toBeTruthy();
 });
 
 it.fail(WEBKIT)('should dispatch drag drop events', async({page, server}) => {
@@ -144,14 +146,14 @@ it.fail(WEBKIT)('should dispatch drag drop events', async({page, server}) => {
   await source.dispatchEvent('dragstart', { dataTransfer });
   const target = await page.$('#target');
   await target.dispatchEvent('drop', { dataTransfer });
-  expect(await page.evaluate(() => {
+  expect(await page.evaluate(({source, target}) => {
     return source.parentElement === target;
-  })).toBeTruthy();
+  }, {source, target})).toBeTruthy();
 });
 
 it('should dispatch click event', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/button.html');
   const button = await page.$('button');
   await button.dispatchEvent('click');
-  expect(await page.evaluate(() => result)).toBe('Clicked');
+  expect(await page.evaluate(() => window['result'])).toBe('Clicked');
 });
diff --git a/test/electron/electron-app.spec.ts b/test/electron/electron-app.spec.ts
index f48d88ea56..0f1265841a 100644
--- a/test/electron/electron-app.spec.ts
+++ b/test/electron/electron-app.spec.ts
@@ -104,7 +104,7 @@ it.skip(!CHROMIUM)('should expose function', async ({ application }) => {
   const t = Date.now();
   await application.context().exposeFunction('add', (a, b) => a + b);
   const page = await application.newBrowserWindow({ width: 800, height: 600 });
-  await page.goto('data:text/html,<script>window.result = add(20, 22);</script>');
+  await page.goto('data:text/html,<script>window["result"] = add(20, 22);</script>');
   expect(await page.evaluate(() => window['result'])).toBe(42);
 });
 
diff --git a/test/elementhandle-bounding-box.spec.js b/test/elementhandle-bounding-box.spec.ts
similarity index 97%
rename from test/elementhandle-bounding-box.spec.js
rename to test/elementhandle-bounding-box.spec.ts
index e71b7c1e78..6d2567b249 100644
--- a/test/elementhandle-bounding-box.spec.js
+++ b/test/elementhandle-bounding-box.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it.fail(FFOX && !HEADLESS)('should work', async ({ page, server }) => {
@@ -67,7 +67,7 @@ it('should work with SVG nodes', async ({ page, server }) => {
 });
 
 it.skip(FFOX)('should work with page scale', async ({ browser, server }) => {
-  const context = await browser.newContext({ viewport: { width: 400, height: 400, isMobile: true } });
+  const context = await browser.newContext({ viewport: { width: 400, height: 400 }, isMobile: true });
   const page = await context.newPage();
   await page.goto(server.PREFIX + '/input/button.html');
   const button = await page.$('button');
diff --git a/test/elementhandle-click.spec.js b/test/elementhandle-click.spec.ts
similarity index 87%
rename from test/elementhandle-click.spec.js
rename to test/elementhandle-click.spec.ts
index eb854a6e90..38bca7874f 100644
--- a/test/elementhandle-click.spec.js
+++ b/test/elementhandle-click.spec.ts
@@ -14,16 +14,16 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should work', async ({ page, server }) => {
   await page.goto(server.PREFIX + '/input/button.html');
   const button = await page.$('button');
   await button.click();
-  expect(await page.evaluate(() => result)).toBe('Clicked');
+  expect(await page.evaluate(() => window['result'])).toBe('Clicked');
 });
 
 it('should work with Node removed', async ({ page, server }) => {
@@ -31,21 +31,21 @@ it('should work with Node removed', async ({ page, server }) => {
   await page.evaluate(() => delete window['Node']);
   const button = await page.$('button');
   await button.click();
-  expect(await page.evaluate(() => result)).toBe('Clicked');
+  expect(await page.evaluate(() => window['result'])).toBe('Clicked');
 });
 
 it('should work for Shadow DOM v1', async ({ page, server }) => {
   await page.goto(server.PREFIX + '/shadow.html');
-  const buttonHandle = await page.evaluateHandle(() => button);
+  const buttonHandle = await page.evaluateHandle(() => window['button'] as HTMLButtonElement);
   await buttonHandle.click();
-  expect(await page.evaluate(() => clicked)).toBe(true);
+  expect(await page.evaluate('clicked')).toBe(true);
 });
 
 it('should work for TextNodes', async ({ page, server }) => {
   await page.goto(server.PREFIX + '/input/button.html');
   const buttonTextNode = await page.evaluateHandle(() => document.querySelector('button').firstChild);
   await buttonTextNode.click();
-  expect(await page.evaluate(() => result)).toBe('Clicked');
+  expect(await page.evaluate(() => window['result'])).toBe('Clicked');
 });
 
 it('should throw for detached nodes', async ({ page, server }) => {
@@ -83,10 +83,10 @@ it('should throw for <br> elements with force', async ({ page, server }) => {
 it('should double click the button', async ({ page, server }) => {
   await page.goto(server.PREFIX + '/input/button.html');
   await page.evaluate(() => {
-    window.double = false;
+    window['double'] = false;
     const button = document.querySelector('button');
     button.addEventListener('dblclick', event => {
-      window.double = true;
+      window['double'] = true;
     });
   });
   const button = await page.$('button');
diff --git a/test/elementhandle-content-frame.spec.js b/test/elementhandle-content-frame.spec.ts
similarity index 97%
rename from test/elementhandle-content-frame.spec.js
rename to test/elementhandle-content-frame.spec.ts
index 9ad8f1096d..8642d22eed 100644
--- a/test/elementhandle-content-frame.spec.js
+++ b/test/elementhandle-content-frame.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should work', async ({ page, server }) => {
diff --git a/test/elementhandle-convenience.spec.js b/test/elementhandle-convenience.spec.ts
similarity index 90%
rename from test/elementhandle-convenience.spec.js
rename to test/elementhandle-convenience.spec.ts
index 091a651123..2e20d5d08d 100644
--- a/test/elementhandle-convenience.spec.js
+++ b/test/elementhandle-convenience.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should have a nice preview', async ({ page, server }) => {
@@ -80,10 +80,10 @@ it('textContent should be atomic', async ({ playwright, page }) => {
         Promise.resolve().then(() => result.textContent = 'modified');
       return result;
     },
-    queryAll(root, selector) {
+    queryAll(root: HTMLElement, selector: string) {
       const result = Array.from(root.querySelectorAll(selector));
       for (const e of result)
-        Promise.resolve().then(() => result.textContent = 'modified');
+        Promise.resolve().then(() => e.textContent = 'modified');
       return result;
     }
   });
@@ -97,16 +97,16 @@ it('textContent should be atomic', async ({ playwright, page }) => {
 it('innerText should be atomic', async ({ playwright, page }) => {
   const createDummySelector = () => ({
     create(root, target) { },
-    query(root, selector) {
+    query(root: HTMLElement, selector: string) {
       const result = root.querySelector(selector);
       if (result)
         Promise.resolve().then(() => result.textContent = 'modified');
       return result;
     },
-    queryAll(root, selector) {
+    queryAll(root: HTMLElement, selector: string) {
       const result = Array.from(root.querySelectorAll(selector));
       for (const e of result)
-        Promise.resolve().then(() => result.textContent = 'modified');
+        Promise.resolve().then(() => e.textContent = 'modified');
       return result;
     }
   });
@@ -126,10 +126,10 @@ it('innerHTML should be atomic', async ({ playwright, page }) => {
         Promise.resolve().then(() => result.textContent = 'modified');
       return result;
     },
-    queryAll(root, selector) {
+    queryAll(root: HTMLElement, selector: string) {
       const result = Array.from(root.querySelectorAll(selector));
       for (const e of result)
-        Promise.resolve().then(() => result.textContent = 'modified');
+        Promise.resolve().then(() => e.textContent = 'modified');
       return result;
     }
   });
@@ -143,16 +143,16 @@ it('innerHTML should be atomic', async ({ playwright, page }) => {
 it('getAttribute should be atomic', async ({ playwright, page }) => {
   const createDummySelector = () => ({
     create(root, target) { },
-    query(root, selector) {
+    query(root: HTMLElement, selector: string) {
       const result = root.querySelector(selector);
       if (result)
         Promise.resolve().then(() => result.setAttribute('foo', 'modified'));
       return result;
     },
-    queryAll(root, selector) {
+    queryAll(root: HTMLElement, selector: string) {
       const result = Array.from(root.querySelectorAll(selector));
       for (const e of result)
-        Promise.resolve().then(() => result.setAttribute('foo', 'modified'));
+        Promise.resolve().then(() => (e as HTMLElement).setAttribute('foo', 'modified'));
       return result;
     }
   });
diff --git a/test/elementhandle-eval-on-selector.spec.js b/test/elementhandle-eval-on-selector.spec.ts
similarity index 85%
rename from test/elementhandle-eval-on-selector.spec.js
rename to test/elementhandle-eval-on-selector.spec.ts
index 4884548502..5d8c72315f 100644
--- a/test/elementhandle-eval-on-selector.spec.js
+++ b/test/elementhandle-eval-on-selector.spec.ts
@@ -14,16 +14,16 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should work', async({page, server}) => {
   await page.setContent('<html><body><div class="tweet"><div class="like">100</div><div class="retweets">10</div></div></body></html>');
   const tweet = await page.$('.tweet');
-  const content = await tweet.$eval('.like', node => node.innerText);
+  const content = await tweet.$eval('.like', node => (node as HTMLElement).innerText);
   expect(content).toBe('100');
 });
 
@@ -31,7 +31,7 @@ it('should retrieve content from subtree', async({page, server}) => {
   const htmlContent = '<div class="a">not-a-child-div</div><div id="myId"><div class="a">a-child-div</div></div>';
   await page.setContent(htmlContent);
   const elementHandle = await page.$('#myId');
-  const content = await elementHandle.$eval('.a', node => node.innerText);
+  const content = await elementHandle.$eval('.a', node => (node as HTMLElement).innerText);
   expect(content).toBe('a-child-div');
 });
 
@@ -39,14 +39,14 @@ it('should throw in case of missing selector', async({page, server}) => {
   const htmlContent = '<div class="a">not-a-child-div</div><div id="myId"></div>';
   await page.setContent(htmlContent);
   const elementHandle = await page.$('#myId');
-  const errorMessage = await elementHandle.$eval('.a', node => node.innerText).catch(error => error.message);
+  const errorMessage = await elementHandle.$eval('.a', node => (node as HTMLElement).innerText).catch(error => error.message);
   expect(errorMessage).toContain(`Error: failed to find element matching selector ".a"`);
 });
 
 it('should work for all', async({page, server}) => {
   await page.setContent('<html><body><div class="tweet"><div class="like">100</div><div class="like">10</div></div></body></html>');
   const tweet = await page.$('.tweet');
-  const content = await tweet.$$eval('.like', nodes => nodes.map(n => n.innerText));
+  const content = await tweet.$$eval('.like', nodes => nodes.map(n => (n as HTMLElement).innerText));
   expect(content).toEqual(['100', '10']);
 });
 
@@ -54,7 +54,7 @@ it('should retrieve content from subtree for all', async({page, server}) => {
   const htmlContent = '<div class="a">not-a-child-div</div><div id="myId"><div class="a">a1-child-div</div><div class="a">a2-child-div</div></div>';
   await page.setContent(htmlContent);
   const elementHandle = await page.$('#myId');
-  const content = await elementHandle.$$eval('.a', nodes => nodes.map(n => n.innerText));
+  const content = await elementHandle.$$eval('.a', nodes => nodes.map(n => (n as HTMLElement).innerText));
   expect(content).toEqual(['a1-child-div', 'a2-child-div']);
 });
 
diff --git a/test/elementhandle-misc.spec.js b/test/elementhandle-misc.spec.ts
similarity index 84%
rename from test/elementhandle-misc.spec.js
rename to test/elementhandle-misc.spec.ts
index 3bdb607ced..5cf08e8471 100644
--- a/test/elementhandle-misc.spec.js
+++ b/test/elementhandle-misc.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should hover', async ({ page, server }) => {
@@ -38,7 +38,7 @@ it('should fill input', async ({ page, server }) => {
   await page.goto(server.PREFIX + '/input/textarea.html');
   const handle = await page.$('input');
   await handle.fill('some value');
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
 });
 
 it('should fill input when Node is removed', async ({ page, server }) => {
@@ -46,29 +46,29 @@ it('should fill input when Node is removed', async ({ page, server }) => {
   await page.evaluate(() => delete window['Node']);
   const handle = await page.$('input');
   await handle.fill('some value');
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
 });
 
 it('should check the box', async ({ page }) => {
   await page.setContent(`<input id='checkbox' type='checkbox'></input>`);
   const input = await page.$('input');
   await input.check();
-  expect(await page.evaluate(() => checkbox.checked)).toBe(true);
+  expect(await page.evaluate('checkbox.checked')).toBe(true);
 });
 
 it('should uncheck the box', async ({ page }) => {
   await page.setContent(`<input id='checkbox' type='checkbox' checked></input>`);
   const input = await page.$('input');
   await input.uncheck();
-  expect(await page.evaluate(() => checkbox.checked)).toBe(false);
+  expect(await page.evaluate('checkbox.checked')).toBe(false);
 });
 
 it('should select single option', async ({ page, server }) => {
   await page.goto(server.PREFIX + '/input/select.html');
   const select = await page.$('select');
   await select.selectOption('blue');
-  expect(await page.evaluate(() => result.onInput)).toEqual(['blue']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['blue']);
 });
 
 it('should focus a button', async ({ page, server }) => {
diff --git a/test/elementhandle-owner-frame.spec.js b/test/elementhandle-owner-frame.spec.ts
similarity index 93%
rename from test/elementhandle-owner-frame.spec.js
rename to test/elementhandle-owner-frame.spec.ts
index 101e3a9d48..6539951a74 100644
--- a/test/elementhandle-owner-frame.spec.js
+++ b/test/elementhandle-owner-frame.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should work', async ({ page, server }) => {
@@ -55,7 +55,7 @@ it('should work for cross-frame evaluations', async ({ page, server }) => {
   await page.goto(server.EMPTY_PAGE);
   await utils.attachFrame(page, 'frame1', server.EMPTY_PAGE);
   const frame = page.mainFrame();
-  const elementHandle = await frame.evaluateHandle(() => document.querySelector('#frame1').contentWindow.document.body);
+  const elementHandle = await frame.evaluateHandle(() => document.querySelector('iframe').contentWindow.document.body);
   expect(await elementHandle.ownerFrame()).toBe(frame.childFrames()[0]);
 });
 
@@ -78,7 +78,7 @@ it('should work for adopted elements', async ({ page, server }) => {
   await page.goto(server.EMPTY_PAGE);
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(url => window.__popup = window.open(url), server.EMPTY_PAGE),
+    page.evaluate(url => window["__popup"] = window.open(url), server.EMPTY_PAGE),
   ]);
   const divHandle = await page.evaluateHandle(() => {
     const div = document.createElement('div');
@@ -89,7 +89,7 @@ it('should work for adopted elements', async ({ page, server }) => {
   await popup.waitForLoadState('domcontentloaded');
   await page.evaluate(() => {
     const div = document.querySelector('div');
-    window.__popup.document.body.appendChild(div);
+    window["__popup"].document.body.appendChild(div);
   });
   expect(await divHandle.ownerFrame()).toBe(popup.mainFrame());
 });
diff --git a/test/elementhandle-press.spec.js b/test/elementhandle-press.spec.ts
similarity index 97%
rename from test/elementhandle-press.spec.js
rename to test/elementhandle-press.spec.ts
index 184e8d001c..6478190501 100644
--- a/test/elementhandle-press.spec.js
+++ b/test/elementhandle-press.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should work', async ({ page }) => {
diff --git a/test/elementhandle-query-selector.spec.js b/test/elementhandle-query-selector.spec.ts
similarity index 94%
rename from test/elementhandle-query-selector.spec.js
rename to test/elementhandle-query-selector.spec.ts
index 55686fb364..9b1d2b1b5e 100644
--- a/test/elementhandle-query-selector.spec.js
+++ b/test/elementhandle-query-selector.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should query existing element', async({page, server}) => {
@@ -41,7 +41,7 @@ it('should work for adopted elements', async({page,server}) => {
   await page.goto(server.EMPTY_PAGE);
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(url => window.__popup = window.open(url), server.EMPTY_PAGE),
+    page.evaluate(url => window["__popup"] = window.open(url), server.EMPTY_PAGE),
   ]);
   const divHandle = await page.evaluateHandle(() => {
     const div = document.createElement('div');
@@ -57,7 +57,7 @@ it('should work for adopted elements', async({page,server}) => {
   await popup.waitForLoadState('domcontentloaded');
   await page.evaluate(() => {
     const div = document.querySelector('div');
-    window.__popup.document.body.appendChild(div);
+    window["__popup"].document.body.appendChild(div);
   });
   expect(await divHandle.$('span')).toBeTruthy();
   expect(await divHandle.$eval('span', e => e.textContent)).toBe('hello');
diff --git a/test/elementhandle-screenshot.spec.js b/test/elementhandle-screenshot.spec.ts
similarity index 98%
rename from test/elementhandle-screenshot.spec.js
rename to test/elementhandle-screenshot.spec.ts
index 67b36971ca..61f9e291b6 100644
--- a/test/elementhandle-screenshot.spec.js
+++ b/test/elementhandle-screenshot.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, USES_HOOKS, HEADLESS} = testOptions;
-const {PNG} = require('pngjs');
+import {PNG} from 'pngjs';
 
 // Firefox headful produces a different image.
 const ffheadful = FFOX && !HEADLESS;
@@ -210,7 +210,7 @@ it.skip(ffheadful)('should work for an element with fractional dimensions', asyn
 });
 
 it.skip(FFOX)('should work with a mobile viewport', async({browser, server}) => {
-  const context = await browser.newContext({viewport: { width: 320, height: 480, isMobile: true }});
+  const context = await browser.newContext({viewport: { width: 320, height: 480 }, isMobile: true});
   const page = await context.newPage();
   await page.goto(server.PREFIX + '/grid.html');
   await page.evaluate(() => window.scrollBy(50, 100));
@@ -288,7 +288,7 @@ it.skip(ffheadful || USES_HOOKS)('should restore viewport after page screenshot
   const page = await context.newPage();
   await page.goto(server.PREFIX + '/grid.html');
   const __testHookBeforeScreenshot = () => { throw new Error('oh my') };
-  const error = await page.screenshot({ fullPage: true, __testHookBeforeScreenshot }).catch(e => e);
+  const error = await page.screenshot({ fullPage: true, __testHookBeforeScreenshot } as any).catch(e => e);
   expect(error.message).toContain('oh my');
   await utils.verifyViewport(page, 350, 360);
   await context.close();
@@ -299,7 +299,7 @@ it.skip(ffheadful || USES_HOOKS)('should restore viewport after page screenshot
   const page = await context.newPage();
   await page.goto(server.PREFIX + '/grid.html');
   const __testHookAfterScreenshot = () => new Promise(f => setTimeout(f, 5000));
-  const error = await page.screenshot({ fullPage: true, __testHookAfterScreenshot, timeout: 3000 }).catch(e => e);
+  const error = await page.screenshot({ fullPage: true, __testHookAfterScreenshot, timeout: 3000 } as any).catch(e => e);
   expect(error.message).toContain('page.screenshot: Timeout 3000ms exceeded');
   await utils.verifyViewport(page, 350, 360);
   await page.setViewportSize({ width: 400, height: 400 });
@@ -310,7 +310,7 @@ it.skip(ffheadful || USES_HOOKS)('should restore viewport after page screenshot
 
 it.skip(ffheadful)('should take element screenshot when default viewport is null and restore back', async({server, browser}) => {
   const context = await browser.newContext({viewport: null});
-  const page = await context.newPage({ viewport: null });
+  const page = await context.newPage();
   await page.setContent(`
     <div style="height: 14px">oooo</div>
     <style>
@@ -344,7 +344,7 @@ it.skip(ffheadful || USES_HOOKS)('should restore viewport after element screensh
   await page.setContent(`<div style="width:600px;height:600px;"></div>`);
   const elementHandle = await page.$('div');
   const __testHookBeforeScreenshot = () => { throw new Error('oh my') };
-  const error = await elementHandle.screenshot({ __testHookBeforeScreenshot }).catch(e => e);
+  const error = await elementHandle.screenshot({ __testHookBeforeScreenshot } as any).catch(e => e);
   expect(error.message).toContain('oh my');
   await utils.verifyViewport(page, 350, 360);
   await context.close();
diff --git a/test/elementhandle-scroll-into-view.spec.js b/test/elementhandle-scroll-into-view.spec.ts
similarity index 98%
rename from test/elementhandle-scroll-into-view.spec.js
rename to test/elementhandle-scroll-into-view.spec.ts
index c7aa663909..7b2725b2f9 100644
--- a/test/elementhandle-scroll-into-view.spec.js
+++ b/test/elementhandle-scroll-into-view.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should work', async ({ page, server }) => {
diff --git a/test/elementhandle-select-text.spec.js b/test/elementhandle-select-text.spec.ts
similarity index 97%
rename from test/elementhandle-select-text.spec.js
rename to test/elementhandle-select-text.spec.ts
index ca3e8a7d34..731a145e3b 100644
--- a/test/elementhandle-select-text.spec.js
+++ b/test/elementhandle-select-text.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should select textarea', async ({ page, server }) => {
diff --git a/test/elementhandle-type.spec.js b/test/elementhandle-type.spec.ts
similarity index 97%
rename from test/elementhandle-type.spec.js
rename to test/elementhandle-type.spec.ts
index bb93914516..07db2ce484 100644
--- a/test/elementhandle-type.spec.js
+++ b/test/elementhandle-type.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { FFOX, HEADLESS } = testOptions;
 
 it('should work', async ({ page }) => {
diff --git a/test/emulation-focus.spec.js b/test/emulation-focus.spec.ts
similarity index 95%
rename from test/emulation-focus.spec.js
rename to test/emulation-focus.spec.ts
index d7cd816a7d..935daa967c 100644
--- a/test/emulation-focus.spec.js
+++ b/test/emulation-focus.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {CHROMIUM, FFOX, MAC, HEADLESS} = testOptions;
 
 it('should think that it is focused by default', async({page}) => {
@@ -66,7 +66,7 @@ it('should provide target for keyboard events', async({page, server}) => {
 it('should not affect mouse event target page', async({page, server}) => {
   const page2 = await page.context().newPage();
   function clickCounter() {
-    document.onclick = () => window.clickCount  = (window.clickCount || 0) + 1;
+    document.onclick = () => window['clickCount']  = (window['clickCount'] || 0) + 1;
   }
   await Promise.all([
     page.evaluate(clickCounter),
@@ -130,9 +130,9 @@ it('should change focused iframe', async({page, server}) => {
     utils.attachFrame(page, 'frame2', server.PREFIX + '/input/textarea.html'),
   ]);
   function logger() {
-    self._events = [];
+    self['_events'] = [];
     const element = document.querySelector('input');
-    element.onfocus = element.onblur = (e) => self._events.push(e.type);
+    element.onfocus = element.onblur = (e) => self['_events'].push(e.type);
   }
   await Promise.all([
     frame1.evaluate(logger),
diff --git a/test/eval-on-selector-all.spec.js b/test/eval-on-selector-all.spec.ts
similarity index 97%
rename from test/eval-on-selector-all.spec.js
rename to test/eval-on-selector-all.spec.ts
index 48a62db0f8..952a2fd26a 100644
--- a/test/eval-on-selector-all.spec.js
+++ b/test/eval-on-selector-all.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should work with css selector', async({page, server}) => {
diff --git a/test/eval-on-selector.spec.js b/test/eval-on-selector.spec.ts
similarity index 99%
rename from test/eval-on-selector.spec.js
rename to test/eval-on-selector.spec.ts
index 6e91381c09..3603cddf5d 100644
--- a/test/eval-on-selector.spec.js
+++ b/test/eval-on-selector.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should work with css selector', async({page, server}) => {
diff --git a/test/firefox/launcher.spec.js b/test/firefox/launcher.spec.ts
similarity index 97%
rename from test/firefox/launcher.spec.js
rename to test/firefox/launcher.spec.ts
index 73c3487dbe..60828fc115 100644
--- a/test/firefox/launcher.spec.js
+++ b/test/firefox/launcher.spec.ts
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('../base.fixture');
+import '../base.fixture';
 
 const { FFOX } = testOptions;
 
diff --git a/test/focus.spec.js b/test/focus.spec.ts
similarity index 78%
rename from test/focus.spec.js
rename to test/focus.spec.ts
index 910d359f41..1c0aca878c 100644
--- a/test/focus.spec.js
+++ b/test/focus.spec.ts
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, LINUX, WEBKIT, MAC} = testOptions;
 
@@ -28,7 +28,7 @@ it('should emit focus event', async function({page, server}) {
   await page.setContent(`<div id=d1 tabIndex=0></div>`);
   let focused = false;
   await page.exposeFunction('focusEvent', () => focused = true);
-  await page.evaluate(() => d1.addEventListener('focus', focusEvent));
+  await page.$eval('#d1', d1 => d1.addEventListener('focus', window['focusEvent']));
   await page.focus('#d1');
   expect(focused).toBe(true);
 });
@@ -40,8 +40,8 @@ it('should emit blur event', async function({page, server}) {
   let blurred = false;
   await page.exposeFunction('focusEvent', () => focused = true);
   await page.exposeFunction('blurEvent', () => blurred = true);
-  await page.evaluate(() => d1.addEventListener('blur', blurEvent));
-  await page.evaluate(() => d2.addEventListener('focus', focusEvent));
+  await page.$eval('#d1', d1 => d1.addEventListener('blur', window['blurEvent']));
+  await page.$eval('#d2', d2 => d2.addEventListener('focus', window['focusEvent']));
   await page.focus('#d2');
   expect(focused).toBe(true);
   expect(blurred).toBe(true);
@@ -51,7 +51,7 @@ it('should traverse focus', async function({page}) {
   await page.setContent(`<input id="i1"><input id="i2">`);
   let focused = false;
   await page.exposeFunction('focusEvent', () => focused = true);
-  await page.evaluate(() => i2.addEventListener('focus', focusEvent));
+  await page.$eval('#i2', i2 => (i2 as HTMLInputElement).addEventListener('focus', window['focusEvent']));
 
   await page.focus('#i1');
   await page.keyboard.type("First");
@@ -59,22 +59,22 @@ it('should traverse focus', async function({page}) {
   await page.keyboard.type("Last");
 
   expect(focused).toBe(true);
-  expect(await page.$eval('#i1', e => e.value)).toBe('First');
-  expect(await page.$eval('#i2', e => e.value)).toBe('Last');
+  expect(await page.$eval('#i1', e => (e as HTMLInputElement).value)).toBe('First');
+  expect(await page.$eval('#i2', e => (e as HTMLInputElement).value)).toBe('Last');
 });
 
 it('should traverse focus in all directions', async function({page}) {
   await page.setContent(`<input value="1"><input value="2"><input value="3">`);
   await page.keyboard.press('Tab');
-  expect(await page.evaluate(() => document.activeElement.value)).toBe('1');
+  expect(await page.evaluate(() => (document.activeElement as HTMLInputElement).value)).toBe('1');
   await page.keyboard.press('Tab');
-  expect(await page.evaluate(() => document.activeElement.value)).toBe('2');
+  expect(await page.evaluate(() => (document.activeElement as HTMLInputElement).value)).toBe('2');
   await page.keyboard.press('Tab');
-  expect(await page.evaluate(() => document.activeElement.value)).toBe('3');
+  expect(await page.evaluate(() => (document.activeElement as HTMLInputElement).value)).toBe('3');
   await page.keyboard.press('Shift+Tab');
-  expect(await page.evaluate(() => document.activeElement.value)).toBe('2');
+  expect(await page.evaluate(() => (document.activeElement as HTMLInputElement).value)).toBe('2');
   await page.keyboard.press('Shift+Tab');
-  expect(await page.evaluate(() => document.activeElement.value)).toBe('1');
+  expect(await page.evaluate(() => (document.activeElement as HTMLInputElement).value)).toBe('1');
 });
 // Chromium and WebKit both have settings for tab traversing all links, but 
 // it is only on by default in WebKit.
diff --git a/test/frame-evaluate.spec.js b/test/frame-evaluate.spec.ts
similarity index 91%
rename from test/frame-evaluate.spec.js
rename to test/frame-evaluate.spec.ts
index c2e890d60b..511f7108ad 100644
--- a/test/frame-evaluate.spec.js
+++ b/test/frame-evaluate.spec.ts
@@ -14,20 +14,20 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
-const path = require('path');
+import utils from './utils';
+import path from 'path';
 const { FFOX, CHROMIUM, WEBKIT, USES_HOOKS } = testOptions;
 
 it('should have different execution contexts', async ({ page, server }) => {
   await page.goto(server.EMPTY_PAGE);
   await utils.attachFrame(page, 'frame1', server.EMPTY_PAGE);
   expect(page.frames().length).toBe(2);
-  await page.frames()[0].evaluate(() => window.FOO = 'foo');
-  await page.frames()[1].evaluate(() => window.FOO = 'bar');
-  expect(await page.frames()[0].evaluate(() => window.FOO)).toBe('foo');
-  expect(await page.frames()[1].evaluate(() => window.FOO)).toBe('bar');
+  await page.frames()[0].evaluate(() => window["FOO"] = 'foo');
+  await page.frames()[1].evaluate(() => window["FOO"] = 'bar');
+  expect(await page.frames()[0].evaluate(() => window["FOO"])).toBe('foo');
+  expect(await page.frames()[1].evaluate(() => window["FOO"])).toBe('bar');
 });
 
 it('should have correct execution contexts', async ({ page, server }) => {
@@ -76,11 +76,11 @@ it('should not allow cross-frame js handles', async ({ page, server }) => {
   const handle = await page.evaluateHandle(() => {
     const iframe = document.querySelector('iframe');
     const foo = { bar: 'baz' };
-    iframe.contentWindow.__foo = foo;
+    iframe.contentWindow['__foo'] = foo;
     return foo;
   });
   const childFrame = page.mainFrame().childFrames()[0];
-  const childResult = await childFrame.evaluate(() => window.__foo);
+  const childResult = await childFrame.evaluate(() => window['__foo']);
   expect(childResult).toEqual({ bar: 'baz' });
   const error = await childFrame.evaluate(foo => foo.bar, handle).catch(e => e);
   expect(error.message).toContain('JSHandles can be evaluated only in the context they were created!');
@@ -117,12 +117,12 @@ it('should be isolated between frames', async({page, server}) => {
   expect(frame1 !== frame2).toBeTruthy();
 
   await Promise.all([
-    frame1.evaluate(() => window.a = 1),
-    frame2.evaluate(() => window.a = 2)
+    frame1.evaluate(() => window["a"] = 1),
+    frame2.evaluate(() => window["a"] = 2)
   ]);
   const [a1, a2] = await Promise.all([
-    frame1.evaluate(() => window.a),
-    frame2.evaluate(() => window.a)
+    frame1.evaluate(() => window['a']),
+    frame2.evaluate(() => window['a'])
   ]);
   expect(a1).toBe(1);
   expect(a2).toBe(2);
diff --git a/test/frame-frame-element.spec.js b/test/frame-frame-element.spec.ts
similarity index 97%
rename from test/frame-frame-element.spec.js
rename to test/frame-frame-element.spec.ts
index ff687b41a3..4e1fae9b39 100644
--- a/test/frame-frame-element.spec.js
+++ b/test/frame-frame-element.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
 it('should work', async({page, server}) => {
diff --git a/test/frame-goto.spec.js b/test/frame-goto.spec.ts
similarity index 96%
rename from test/frame-goto.spec.js
rename to test/frame-goto.spec.ts
index 930396ba89..a67b2b9d7b 100644
--- a/test/frame-goto.spec.js
+++ b/test/frame-goto.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
-const path = require('path');
-const url = require('url');
+import utils from './utils';
+import path from 'path';
+import url from 'url';
 const {FFOX, CHROMIUM, WEBKIT, ASSETS_DIR, MAC, WIN} = testOptions;
 
 it('should navigate subframes', async({page, server}) => {
diff --git a/test/frame-hierarchy.spec.js b/test/frame-hierarchy.spec.ts
similarity index 96%
rename from test/frame-hierarchy.spec.js
rename to test/frame-hierarchy.spec.ts
index de87206e69..ea8b85b493 100644
--- a/test/frame-hierarchy.spec.js
+++ b/test/frame-hierarchy.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
 it('should handle nested frames', async({page, server}) => {
@@ -43,7 +43,7 @@ it('should send events when frames are manipulated dynamically', async({page, se
   const navigatedFrames = [];
   page.on('framenavigated', frame => navigatedFrames.push(frame));
   await page.evaluate(() => {
-    const frame = document.getElementById('frame1');
+    const frame = document.getElementById('frame1') as HTMLIFrameElement;
     frame.src = './empty.html';
     return new Promise(x => frame.onload = x);
   });
@@ -161,13 +161,13 @@ it('should report frame.parent()', async({page, server}) => {
 it('should report different frame instance when frame re-attaches', async({page, server}) => {
   const frame1 = await utils.attachFrame(page, 'frame1', server.EMPTY_PAGE);
   await page.evaluate(() => {
-    window.frame = document.querySelector('#frame1');
-    window.frame.remove();
+    window['frame'] = document.querySelector('#frame1');
+    window['frame'].remove();
   });
   expect(frame1.isDetached()).toBe(true);
   const [frame2] = await Promise.all([
     page.waitForEvent('frameattached'),
-    page.evaluate(() => document.body.appendChild(window.frame)),
+    page.evaluate(() => document.body.appendChild(window['frame'])),
   ]);
   expect(frame2.isDetached()).toBe(false);
   expect(frame1).not.toBe(frame2);
diff --git a/test/geolocation.spec.js b/test/geolocation.spec.ts
similarity index 95%
rename from test/geolocation.spec.js
rename to test/geolocation.spec.ts
index 1a8dfa9cea..e50c6837d6 100644
--- a/test/geolocation.spec.js
+++ b/test/geolocation.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
@@ -75,7 +75,7 @@ it('should isolate contexts', async({page, server, context, browser}) => {
 it('should throw with missing latitude', async({context}) => {
   let error = null;
   try {
-    await context.setGeolocation({longitude: 10});
+    await context.setGeolocation({longitude: 10} as any);
   } catch (e) {
     error = e;
   }
@@ -94,7 +94,7 @@ it('should not modify passed default options object', async({browser}) => {
 it('should throw with missing longitude in default options', async({browser}) => {
   let error = null;
   try {
-    const context = await browser.newContext({ geolocation: {latitude: 10} });
+    const context = await browser.newContext({ geolocation: {latitude: 10} as any });
     await context.close();
   } catch (e) {
     error = e;
@@ -149,9 +149,9 @@ it('should use context options for popup', async({page, context, server}) => {
   await context.setGeolocation({ longitude: 10, latitude: 10 });
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(url => window._popup = window.open(url), server.PREFIX + '/geolocation.html'),
+    page.evaluate(url => window["_popup"] = window.open(url), server.PREFIX + '/geolocation.html'),
   ]);
   await popup.waitForLoadState();
-  const geolocation = await popup.evaluate(() => window.geolocationPromise);
+  const geolocation = await popup.evaluate(() => window['geolocationPromise']);
   expect(geolocation).toEqual({ longitude: 10, latitude: 10 });
 });
diff --git a/test/headful.spec.js b/test/headful.spec.ts
similarity index 99%
rename from test/headful.spec.js
rename to test/headful.spec.ts
index 046357b54a..bd1b67e5ae 100644
--- a/test/headful.spec.js
+++ b/test/headful.spec.ts
@@ -13,9 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const { makeUserDataDir, removeUserDataDir } = utils;
 const {FFOX, CHROMIUM, WEBKIT, WIN, MAC} = testOptions;
 
diff --git a/test/ignorehttpserrors.spec.js b/test/ignorehttpserrors.spec.ts
similarity index 99%
rename from test/ignorehttpserrors.spec.js
rename to test/ignorehttpserrors.spec.ts
index 27df266bb7..9d24a6474d 100644
--- a/test/ignorehttpserrors.spec.js
+++ b/test/ignorehttpserrors.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT, MAC} = testOptions;
 
diff --git a/test/interception.spec.js b/test/interception.spec.ts
similarity index 91%
rename from test/interception.spec.js
rename to test/interception.spec.ts
index ef5db79fba..5f1b34b5b9 100644
--- a/test/interception.spec.js
+++ b/test/interception.spec.ts
@@ -14,12 +14,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const { helper } = require('../lib/helper');
-const vm = require('vm');
+import fs from 'fs';
+import path from 'path';
+import { helper } from '../lib/helper';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, HEADLESS} = testOptions;
 
 it('should work with navigation', async({page, server}) => {
@@ -48,10 +48,10 @@ it('should work with ignoreHTTPSErrors', async({browser, httpsServer}) => {
 
 it('should intercept after a service worker', async({browser, page, server, context}) => {
   await page.goto(server.PREFIX + '/serviceworkers/fetchdummy/sw.html');
-  await page.evaluate(() => window.activationPromise);
+  await page.evaluate(() => window["activationPromise"]);
 
   // Sanity check.
-  const swResponse = await page.evaluate(() => fetchDummy('foo'));
+  const swResponse = await page.evaluate(() => window["fetchDummy"]('foo'));
   expect(swResponse).toBe('responseFromServiceWorker:foo');
 
   await page.route('**/foo', route => {
@@ -65,11 +65,11 @@ it('should intercept after a service worker', async({browser, page, server, cont
   });
 
   // Page route is applied after service worker fetch event.
-  const swResponse2 = await page.evaluate(() => fetchDummy('foo'));
+  const swResponse2 = await page.evaluate(() => window["fetchDummy"]('foo'));
   expect(swResponse2).toBe('responseFromServiceWorker:foo');
 
   // Page route is not applied to service worker initiated fetch.
-  const nonInterceptedResponse = await page.evaluate(() => fetchDummy('passthrough'));
+  const nonInterceptedResponse = await page.evaluate(() => window["fetchDummy"]('passthrough'));
   expect(nonInterceptedResponse).toBe('FAILURE: Not Found');
 });
 
diff --git a/test/jshandle-as-element.spec.js b/test/jshandle-as-element.spec.ts
similarity index 93%
rename from test/jshandle-as-element.spec.js
rename to test/jshandle-as-element.spec.ts
index e904d99a2b..aa0b8fa4ed 100644
--- a/test/jshandle-as-element.spec.js
+++ b/test/jshandle-as-element.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
@@ -35,7 +35,7 @@ it('should return ElementHandle for TextNodes', async({page, server}) => {
   const aHandle = await page.evaluateHandle(() => document.querySelector('div').firstChild);
   const element = aHandle.asElement();
   expect(element).toBeTruthy();
-  expect(await page.evaluate(e => e.nodeType === HTMLElement.TEXT_NODE, element)).toBeTruthy();
+  expect(await page.evaluate(e => e.nodeType === Node.TEXT_NODE, element)).toBeTruthy();
 });
 
 it('should work with nullified Node', async({page, server}) => {
diff --git a/test/jshandle-evaluate.spec.js b/test/jshandle-evaluate.spec.ts
similarity index 87%
rename from test/jshandle-evaluate.spec.js
rename to test/jshandle-evaluate.spec.ts
index b26bf7ccc8..09881b4826 100644
--- a/test/jshandle-evaluate.spec.js
+++ b/test/jshandle-evaluate.spec.ts
@@ -14,21 +14,21 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
 it('should work with function', async({page, server}) => {
   const windowHandle = await page.evaluateHandle(() => {
-    window.foo = [1, 2];
+    window['foo'] = [1, 2];
     return window;
   });
-  expect(await windowHandle.evaluate(w => w.foo)).toEqual([1, 2]);
+  expect(await windowHandle.evaluate(w => w['foo'])).toEqual([1, 2]);
 });
 
 it('should work with expression', async({page, server}) => {
   const windowHandle = await page.evaluateHandle(() => {
-    window.foo = [1, 2];
+    window['foo'] = [1, 2];
     return window;
   });
   expect(await windowHandle.evaluate('window.foo')).toEqual([1, 2]);
diff --git a/test/jshandle-json-value.spec.js b/test/jshandle-json-value.spec.ts
similarity index 98%
rename from test/jshandle-json-value.spec.js
rename to test/jshandle-json-value.spec.ts
index 73529b8678..73d4c00033 100644
--- a/test/jshandle-json-value.spec.js
+++ b/test/jshandle-json-value.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
diff --git a/test/jshandle-properties.spec.js b/test/jshandle-properties.spec.ts
similarity index 98%
rename from test/jshandle-properties.spec.js
rename to test/jshandle-properties.spec.ts
index 90328cfc66..e5e6df2e68 100644
--- a/test/jshandle-properties.spec.js
+++ b/test/jshandle-properties.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
@@ -77,11 +77,13 @@ it('getProperties should return empty map for non-objects', async({page, server}
 it('getProperties should return even non-own properties', async({page, server}) => {
   const aHandle = await page.evaluateHandle(() => {
     class A {
+      a: string;
       constructor() {
         this.a = '1';
       }
     }
     class B extends A {
+      b: string;
       constructor() {
         super();
         this.b = '2';
diff --git a/test/jshandle-to-string.spec.js b/test/jshandle-to-string.spec.ts
similarity index 99%
rename from test/jshandle-to-string.spec.js
rename to test/jshandle-to-string.spec.ts
index 84834de2b7..cdf70895e6 100644
--- a/test/jshandle-to-string.spec.js
+++ b/test/jshandle-to-string.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
diff --git a/test/keyboard.spec.js b/test/keyboard.spec.ts
similarity index 97%
rename from test/keyboard.spec.js
rename to test/keyboard.spec.ts
index ed6bdb21bf..ee3bc24e0b 100644
--- a/test/keyboard.spec.js
+++ b/test/keyboard.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 
 const {FFOX, WEBKIT, CHROMIUM, MAC} = testOptions;
 
@@ -278,10 +278,10 @@ it('should press Enter', async ({page, server}) => {
   async function testEnterKey(key, expectedKey, expectedCode) {
     await page.keyboard.press(key);
     const lastEvent = await lastEventHandle.jsonValue();
-    expect(lastEvent.key).toBe(expectedKey, `${JSON.stringify(key)} had the wrong key: ${lastEvent.key}`);
-    expect(lastEvent.code).toBe(expectedCode, `${JSON.stringify(key)} had the wrong code: ${lastEvent.code}`);
+    expect(lastEvent.key).toBe(expectedKey); // had the wrong key
+    expect(lastEvent.code).toBe(expectedCode); // had the wrong code
     const value = await page.$eval('textarea', t => t.value);
-    expect(value).toBe('\n', `${JSON.stringify(key)} failed to create a newline: ${JSON.stringify(value)}`);
+    expect(value).toBe('\n'); // failed to create a newline
     await page.$eval('textarea', t => t.value = '');
   }
 });
@@ -428,7 +428,7 @@ async function captureLastKeydown(page) {
       lastEvent.code = e.code;
       lastEvent.metaKey = e.metaKey;
       // keyIdentifier only exists in WebKit, and isn't in TypeScript's lib.
-      lastEvent.keyIdentifier = 'keyIdentifier' in e && e.keyIdentifier;
+      lastEvent.keyIdentifier = 'keyIdentifier' in e && e['keyIdentifier'];
     }, true);
     return lastEvent;
   });
diff --git a/test/launcher.spec.js b/test/launcher.spec.ts
similarity index 91%
rename from test/launcher.spec.js
rename to test/launcher.spec.ts
index f6f52f0821..4bf75b5344 100644
--- a/test/launcher.spec.js
+++ b/test/launcher.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const fs = require('fs');
-const utils = require('./utils');
+import path from 'path';
+import fs from 'fs';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should require top-level Errors', async({playwright}) => {
diff --git a/test/logger.spec.js b/test/logger.spec.ts
similarity index 96%
rename from test/logger.spec.js
rename to test/logger.spec.ts
index 724fa7c85c..19fd972d9a 100644
--- a/test/logger.spec.js
+++ b/test/logger.spec.ts
@@ -13,10 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
+import fs from 'fs';
+import path from 'path';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL} = testOptions;
 
 it('should log', async({browserType, defaultBrowserOptions}) => {
diff --git a/test/mouse.spec.js b/test/mouse.spec.ts
similarity index 89%
rename from test/mouse.spec.js
rename to test/mouse.spec.ts
index d29c3a3551..779d44cf70 100644
--- a/test/mouse.spec.js
+++ b/test/mouse.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT, MAC, WIN} = testOptions;
 
@@ -31,7 +31,7 @@ function dimensions() {
 it.fail(FFOX && WIN)('should click the document', async({page, server}) => {
   // Occasionally times out on FFOX on Windows: https://github.com/microsoft/playwright/pull/1911/checks?check_run_id=607149016
   await page.evaluate(() => {
-    window.clickPromise = new Promise(resolve => {
+    window["clickPromise"] = new Promise(resolve => {
       document.addEventListener('click', event => {
         resolve({
           type: event.type,
@@ -45,7 +45,7 @@ it.fail(FFOX && WIN)('should click the document', async({page, server}) => {
     });
   });
   await page.mouse.click(50, 60);
-  const event = await page.evaluate(() => window.clickPromise);
+  const event = await page.evaluate(() => window["clickPromise"]);
   expect(event.type).toBe('click');
   expect(event.detail).toBe(1);
   expect(event.clientX).toBe(50);
@@ -57,7 +57,7 @@ it.fail(FFOX && WIN)('should click the document', async({page, server}) => {
 it('should dblclick the div', async({page, server}) => {
   await page.setContent(`<div style='width: 100px; height: 100px;'>Click me</div>`);
   await page.evaluate(() => {
-    window.dblclickPromise = new Promise(resolve => {
+    window["dblclickPromise"] = new Promise(resolve => {
       document.querySelector('div').addEventListener('dblclick', event => {
         resolve({
           type: event.type,
@@ -71,7 +71,7 @@ it('should dblclick the div', async({page, server}) => {
     });
   });
   await page.mouse.dblclick(50, 60);
-  const event = await page.evaluate(() => window.dblclickPromise);
+  const event = await page.evaluate(() => window["dblclickPromise"]);
   expect(event.type).toBe('dblclick');
   expect(event.detail).toBe(2);
   expect(event.clientX).toBe(50);
@@ -118,7 +118,7 @@ it('should trigger hover state with removed window.Node', async({page, server})
 
 it('should set modifier keys on click', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/scrollable.html');
-  await page.evaluate(() => document.querySelector('#button-3').addEventListener('mousedown', e => window.lastEvent = e, true));
+  await page.evaluate(() => document.querySelector('#button-3').addEventListener('mousedown', e => window["lastEvent"] = e, true));
   const modifiers = {'Shift': 'shiftKey', 'Control': 'ctrlKey', 'Alt': 'altKey', 'Meta': 'metaKey'};
   // In Firefox, the Meta modifier only exists on Mac
   if (FFOX && !MAC)
@@ -126,13 +126,13 @@ it('should set modifier keys on click', async({page, server}) => {
   for (const modifier in modifiers) {
     await page.keyboard.down(modifier);
     await page.click('#button-3');
-    if (!(await page.evaluate(mod => window.lastEvent[mod], modifiers[modifier])))
+    if (!(await page.evaluate(mod => window["lastEvent"][mod], modifiers[modifier])))
       throw new Error(modifiers[modifier] + ' should be true');
     await page.keyboard.up(modifier);
   }
   await page.click('#button-3');
   for (const modifier in modifiers) {
-    if ((await page.evaluate(mod => window.lastEvent[mod], modifiers[modifier])))
+    if ((await page.evaluate(mod => window["lastEvent"][mod], modifiers[modifier])))
       throw new Error(modifiers[modifier] + ' should be false');
   }
 });
@@ -143,9 +143,9 @@ it('should tween mouse movement', async({page, server}) => {
     await page.evaluate(() => new Promise(requestAnimationFrame));
   await page.mouse.move(100, 100);
   await page.evaluate(() => {
-    window.result = [];
+    window["result"] = [];
     document.addEventListener('mousemove', event => {
-      window.result.push([event.clientX, event.clientY]);
+      window["result"].push([event.clientX, event.clientY]);
     });
   });
   await page.mouse.move(200, 300, {steps: 5});
@@ -160,13 +160,13 @@ it('should tween mouse movement', async({page, server}) => {
 
 it.skip(FFOX)('should work with mobile viewports and cross process navigations', async({browser, server}) => {
   // @see https://crbug.com/929806
-  const context = await browser.newContext({ viewport: {width: 360, height: 640, isMobile: true} });
+  const context = await browser.newContext({ viewport: {width: 360, height: 640}, isMobile: true });
   const page = await context.newPage();
   await page.goto(server.EMPTY_PAGE);
   await page.goto(server.CROSS_PROCESS_PREFIX + '/mobile.html');
   await page.evaluate(() => {
     document.addEventListener('click', event => {
-      window.result = {x: event.clientX, y: event.clientY};
+      window["result"] = {x: event.clientX, y: event.clientY};
     });
   });
 
@@ -183,6 +183,6 @@ xdescribe('Drag and Drop', function() {
     await page.mouse.down();
     await page.hover('#target');
     await page.mouse.up();
-    expect(await page.$eval('#target', target => target.contains(document.querySelector('#source')))).toBe(true, 'could not find source in target');
+    expect(await page.$eval('#target', target => target.contains(document.querySelector('#source')))).toBe(true); // could not find source in target
   })
 });
diff --git a/test/multiclient.spec.js b/test/multiclient.spec.ts
similarity index 97%
rename from test/multiclient.spec.js
rename to test/multiclient.spec.ts
index 05044b17ec..c17c112315 100644
--- a/test/multiclient.spec.js
+++ b/test/multiclient.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
@@ -83,7 +83,7 @@ it('should be able to connect multiple times to the same browser', async({browse
   browser1.close();
 
   const page2 = await browser2.newPage();
-  expect(await page2.evaluate(() => 7 * 6)).toBe(42, 'original browser should still work');
+  expect(await page2.evaluate(() => 7 * 6)).toBe(42); // original browser should still work
   await browser2.close();
   if (toImpl)
     await toImpl(browserServer)._checkLeaks();
diff --git a/test/navigation.spec.js b/test/navigation.spec.ts
similarity index 97%
rename from test/navigation.spec.js
rename to test/navigation.spec.ts
index 46f6f4585f..a511fa59b8 100644
--- a/test/navigation.spec.js
+++ b/test/navigation.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 it('should work with _blank target', async({page, server}) => {
   server.setRoute('/empty.html', (req, res) => {
diff --git a/test/network-request.spec.js b/test/network-request.spec.ts
similarity index 98%
rename from test/network-request.spec.js
rename to test/network-request.spec.ts
index 3110c5c4ed..979014c86f 100644
--- a/test/network-request.spec.js
+++ b/test/network-request.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const utils = require('./utils');
+import fs from 'fs';
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, MAC, WIN} = testOptions;
 
 it('should work for main frame navigation request', async({page, server}) => {
diff --git a/test/network-response.spec.js b/test/network-response.spec.ts
similarity index 97%
rename from test/network-response.spec.js
rename to test/network-response.spec.ts
index a6c8ce9b3d..e238a8e130 100644
--- a/test/network-response.spec.js
+++ b/test/network-response.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const utils = require('./utils');
+import fs from 'fs';
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, MAC, WIN} = testOptions;
 
 it('should work', async({page, server}) => {
diff --git a/test/page-add-init-script.spec.js b/test/page-add-init-script.spec.ts
similarity index 69%
rename from test/page-add-init-script.spec.js
rename to test/page-add-init-script.spec.ts
index 8be88d117d..6ef506afaa 100644
--- a/test/page-add-init-script.spec.js
+++ b/test/page-add-init-script.spec.ts
@@ -14,44 +14,44 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
-const path = require('path');
+import utils from './utils';
+import path from 'path';
 const { FFOX, CHROMIUM, WEBKIT, USES_HOOKS } = testOptions;
 
 it('should evaluate before anything else on the page', async ({ page, server }) => {
   await page.addInitScript(function () {
-    window.injected = 123;
+    window["injected"] = 123;
   });
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.result)).toBe(123);
+  expect(await page.evaluate(() => window["result"])).toBe(123);
 });
 
 it('should work with a path', async ({ page, server }) => {
   await page.addInitScript({ path: path.join(__dirname, 'assets/injectedfile.js') });
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.result)).toBe(123);
+  expect(await page.evaluate(() => window["result"])).toBe(123);
 });
 
 it('should work with content', async ({ page, server }) => {
-  await page.addInitScript({ content: 'window.injected = 123' });
+  await page.addInitScript({ content: 'window["injected"] = 123' });
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.result)).toBe(123);
+  expect(await page.evaluate(() => window["result"])).toBe(123);
 });
 
 it('should throw without path and content', async ({ page, server }) => {
-  const error = await page.addInitScript({ foo: 'bar' }).catch(e => e);
+  const error = await page.addInitScript({ foo: 'bar' } as any).catch(e => e);
   expect(error.message).toContain('Either path or content property must be present');
 });
 
 it('should work with browser context scripts', async ({ browser, server }) => {
   const context = await browser.newContext();
-  await context.addInitScript(() => window.temp = 123);
+  await context.addInitScript(() => window["temp"] = 123);
   const page = await context.newPage();
-  await page.addInitScript(() => window.injected = window.temp);
+  await page.addInitScript(() => window["injected"] = window["temp"]);
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.result)).toBe(123);
+  expect(await page.evaluate(() => window["result"])).toBe(123);
   await context.close();
 });
 
@@ -60,50 +60,50 @@ it('should work with browser context scripts with a path', async ({ browser, ser
   await context.addInitScript({ path: path.join(__dirname, 'assets/injectedfile.js') });
   const page = await context.newPage();
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.result)).toBe(123);
+  expect(await page.evaluate(() => window["result"])).toBe(123);
   await context.close();
 });
 
 it('should work with browser context scripts for already created pages', async ({ browser, server }) => {
   const context = await browser.newContext();
   const page = await context.newPage();
-  await context.addInitScript(() => window.temp = 123);
-  await page.addInitScript(() => window.injected = window.temp);
+  await context.addInitScript(() => window["temp"] = 123);
+  await page.addInitScript(() => window["injected"] = window["temp"]);
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.result)).toBe(123);
+  expect(await page.evaluate(() => window["result"])).toBe(123);
   await context.close();
 });
 
 it('should support multiple scripts', async ({ page, server }) => {
   await page.addInitScript(function () {
-    window.script1 = 1;
+    window["script1"] = 1;
   });
   await page.addInitScript(function () {
-    window.script2 = 2;
+    window["script2"] = 2;
   });
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.script1)).toBe(1);
-  expect(await page.evaluate(() => window.script2)).toBe(2);
+  expect(await page.evaluate(() => window["script1"])).toBe(1);
+  expect(await page.evaluate(() => window["script2"])).toBe(2);
 });
 
 it('should work with CSP', async ({ page, server }) => {
   server.setCSP('/empty.html', 'script-src ' + server.PREFIX);
   await page.addInitScript(function () {
-    window.injected = 123;
+    window["injected"] = 123;
   });
   await page.goto(server.PREFIX + '/empty.html');
-  expect(await page.evaluate(() => window.injected)).toBe(123);
+  expect(await page.evaluate(() => window["injected"])).toBe(123);
 
   // Make sure CSP works.
   await page.addScriptTag({ content: 'window.e = 10;' }).catch(e => void e);
-  expect(await page.evaluate(() => window.e)).toBe(undefined);
+  expect(await page.evaluate(() => window['e'])).toBe(undefined);
 });
 
 it('should work after a cross origin navigation', async ({ page, server }) => {
   await page.goto(server.CROSS_PROCESS_PREFIX);
   await page.addInitScript(function () {
-    window.injected = 123;
+    window["injected"] = 123;
   });
   await page.goto(server.PREFIX + '/tamperable.html');
-  expect(await page.evaluate(() => window.result)).toBe(123);
+  expect(await page.evaluate(() => window["result"])).toBe(123);
 });
diff --git a/test/page-add-script-tag.spec.js b/test/page-add-script-tag.spec.ts
similarity index 84%
rename from test/page-add-script-tag.spec.js
rename to test/page-add-script-tag.spec.ts
index 362b6ea110..4f87aec23d 100644
--- a/test/page-add-script-tag.spec.js
+++ b/test/page-add-script-tag.spec.ts
@@ -14,16 +14,17 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should throw an error if no options are provided', async({page, server}) => {
   let error = null;
   try {
+    //@ts-ignore
     await page.addScriptTag('/injectedfile.js');
   } catch (e) {
     error = e;
@@ -35,27 +36,27 @@ it('should work with a url', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   const scriptHandle = await page.addScriptTag({ url: '/injectedfile.js' });
   expect(scriptHandle.asElement()).not.toBeNull();
-  expect(await page.evaluate(() => __injected)).toBe(42);
+  expect(await page.evaluate(() => window['__injected'])).toBe(42);
 });
 
 it('should work with a url and type=module', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   await page.addScriptTag({ url: '/es6/es6import.js', type: 'module' });
-  expect(await page.evaluate(() => __es6injected)).toBe(42);
+  expect(await page.evaluate(() => window['__es6injected'])).toBe(42);
 });
 
 it('should work with a path and type=module', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   await page.addScriptTag({ path: path.join(__dirname, 'assets/es6/es6pathimport.js'), type: 'module' });
   await page.waitForFunction('window.__es6injected');
-  expect(await page.evaluate(() => __es6injected)).toBe(42);
+  expect(await page.evaluate(() => window['__es6injected'])).toBe(42);
 });
 
 it('should work with a content and type=module', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   await page.addScriptTag({ content: `import num from '/es6/es6module.js';window.__es6injected = num;`, type: 'module' });
   await page.waitForFunction('window.__es6injected');
-  expect(await page.evaluate(() => __es6injected)).toBe(42);
+  expect(await page.evaluate(() => window['__es6injected'])).toBe(42);
 });
 
 it('should throw an error if loading from url fail', async({page, server}) => {
@@ -73,28 +74,28 @@ it('should work with a path', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   const scriptHandle = await page.addScriptTag({ path: path.join(__dirname, 'assets/injectedfile.js') });
   expect(scriptHandle.asElement()).not.toBeNull();
-  expect(await page.evaluate(() => __injected)).toBe(42);
+  expect(await page.evaluate(() => window['__injected'])).toBe(42);
 });
 
 it.skip(WEBKIT)('should include sourceURL when path is provided', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   await page.addScriptTag({ path: path.join(__dirname, 'assets/injectedfile.js') });
-  const result = await page.evaluate(() => __injectedError.stack);
+  const result = await page.evaluate(() => window['__injectedError'].stack);
   expect(result).toContain(path.join('assets', 'injectedfile.js'));
 });
 
 it('should work with content', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
-  const scriptHandle = await page.addScriptTag({ content: 'window.__injected = 35;' });
+  const scriptHandle = await page.addScriptTag({ content: 'window["__injected"] = 35;' });
   expect(scriptHandle.asElement()).not.toBeNull();
-  expect(await page.evaluate(() => __injected)).toBe(35);
+  expect(await page.evaluate(() => window['__injected'])).toBe(35);
 });
 
 it.fail(FFOX)('should throw when added with content to the CSP page', async({page, server}) => {
   // Firefox fires onload for blocked script before it issues the CSP console error.
   await page.goto(server.PREFIX + '/csp.html');
   let error = null;
-  await page.addScriptTag({ content: 'window.__injected = 35;' }).catch(e => error = e);
+  await page.addScriptTag({ content: 'window["__injected"] = 35;' }).catch(e => error = e);
   expect(error).toBeTruthy();
 });
 
diff --git a/test/page-add-style-tag.spec.js b/test/page-add-style-tag.spec.ts
similarity index 96%
rename from test/page-add-style-tag.spec.js
rename to test/page-add-style-tag.spec.ts
index 457b076350..7a786edc39 100644
--- a/test/page-add-style-tag.spec.js
+++ b/test/page-add-style-tag.spec.ts
@@ -14,16 +14,17 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should throw an error if no options are provided', async({page, server}) => {
   let error = null;
   try {
+    //@ts-ignore
     await page.addStyleTag('/injectedstyle.css');
   } catch (e) {
     error = e;
diff --git a/test/page-basic.spec.js b/test/page-basic.spec.ts
similarity index 98%
rename from test/page-basic.spec.js
rename to test/page-basic.spec.ts
index f96696246b..b4faf06cf5 100644
--- a/test/page-basic.spec.js
+++ b/test/page-basic.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should reject all promises when page is closed', async({context}) => {
diff --git a/test/page-emulate-media.spec.js b/test/page-emulate-media.spec.ts
similarity index 95%
rename from test/page-emulate-media.spec.js
rename to test/page-emulate-media.spec.ts
index ec0cfd4cc2..e695c91d0c 100644
--- a/test/page-emulate-media.spec.js
+++ b/test/page-emulate-media.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {CHROMIUM, FFOX, MAC, HEADLESS} = testOptions;
 
 it('should emulate type', async({page, server}) => {
@@ -35,7 +35,7 @@ it('should emulate type', async({page, server}) => {
 
 it('should throw in case of bad type argument', async({page, server}) => {
   let error = null;
-  await page.emulateMedia({ media: 'bad' }).catch(e => error = e);
+  await page.emulateMedia({ media: 'bad' as any}).catch(e => error = e);
   expect(error.message).toContain('media: expected one of (screen|print|null)');
 });
 
@@ -63,7 +63,7 @@ it('should default to light', async({page, server}) => {
 
 it('should throw in case of bad argument', async({page, server}) => {
   let error = null;
-  await page.emulateMedia({ colorScheme: 'bad' }).catch(e => error = e);
+  await page.emulateMedia({ colorScheme: 'bad' as any}).catch(e => error = e);
   expect(error.message).toContain('colorScheme: expected one of (dark|light|no-preference|null)');
 });
 
@@ -72,7 +72,7 @@ it('should work during navigation', async({page, server}) => {
   const navigated = page.goto(server.EMPTY_PAGE);
   for (let i = 0; i < 9; i++) {
     await Promise.all([
-      page.emulateMedia({ colorScheme: ['dark', 'light'][i & 1] }),
+      page.emulateMedia({ colorScheme: (['dark', 'light'] as const)[i & 1] }),
       new Promise(f => setTimeout(f, 1)),
     ]);
   }
diff --git a/test/page-evaluate-handle.spec.js b/test/page-evaluate-handle.spec.ts
similarity index 96%
rename from test/page-evaluate-handle.spec.js
rename to test/page-evaluate-handle.spec.ts
index 7b9062f2af..7f894c4de1 100644
--- a/test/page-evaluate-handle.spec.js
+++ b/test/page-evaluate-handle.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
@@ -66,7 +66,7 @@ it('should accept multiple nested handles', async({page, server}) => {
 
 it('should throw for circular objects', async({page, server}) => {
   const a = { x: 1 };
-  a.y = a;
+  a['y'] = a;
   const error = await page.evaluate(x => x, a).catch(e => e);
   expect(error.message).toContain('Argument is a circular structure');
 });
@@ -103,8 +103,8 @@ it('should pass configurable args', async({page, server}) => {
 
 it('should work with primitives', async({page, server}) => {
   const aHandle = await page.evaluateHandle(() => {
-    window.FOO = 123;
+    window['FOO'] = 123;
     return window;
   });
-  expect(await page.evaluate(e => e.FOO, aHandle)).toBe(123);
+  expect(await page.evaluate(e => e['FOO'], aHandle)).toBe(123);
 });
diff --git a/test/page-evaluate.spec.js b/test/page-evaluate.spec.ts
similarity index 93%
rename from test/page-evaluate.spec.js
rename to test/page-evaluate.spec.ts
index ea63280f72..3bcd5e0343 100644
--- a/test/page-evaluate.spec.js
+++ b/test/page-evaluate.spec.ts
@@ -14,11 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
-const path = require('path');
-const { FFOX, CHROMIUM, WEBKIT, USES_HOOKS } = testOptions;
+const {WEBKIT, USES_HOOKS, FFOX} = testOptions;
 
 it('should work', async ({ page, server }) => {
   const result = await page.evaluate(() => 7 * 3);
@@ -102,7 +100,7 @@ it('should transfer maps as empty objects', async ({ page, server }) => {
 });
 
 it('should modify global environment', async ({ page }) => {
-  await page.evaluate(() => window.globalVar = 123);
+  await page.evaluate(() => window['globalVar'] = 123);
   expect(await page.evaluate('globalVar')).toBe(123);
 });
 
@@ -176,13 +174,14 @@ it('should work from-inside an exposed function', async ({ page, server }) => {
     return await page.evaluate(({ a, b }) => a * b, { a, b });
   });
   const result = await page.evaluate(async function () {
-    return await callController(9, 3);
+    return await window['callController'](9, 3);
   });
   expect(result).toBe(27);
 });
 
 it('should reject promise with exception', async ({ page, server }) => {
   let error = null;
+  //@ts-ignore
   await page.evaluate(() => not_existing_object.property).catch(e => error = e);
   expect(error).toBeTruthy();
   expect(error.message).toContain('not_existing_object');
@@ -233,17 +232,18 @@ it('should work with overwritten Promise', async ({ page, server }) => {
   await page.evaluate(() => {
     const originalPromise = window.Promise;
     class Promise2 {
-      static all(...arg) {
-        return wrap(originalPromise.all(...arg));
+      _promise: Promise<any>;
+      static all(arg) {
+        return wrap(originalPromise.all(arg));
       }
-      static race(...arg) {
-        return wrap(originalPromise.race(...arg));
+      static race(arg) {
+        return wrap(originalPromise.race(arg));
       }
-      static resolve(...arg) {
-        return wrap(originalPromise.resolve(...arg));
+      static resolve(arg) {
+        return wrap(originalPromise.resolve(arg));
       }
-      constructor(f, r) {
-        this._promise = new originalPromise(f, r);
+      constructor(f) {
+        this._promise = new originalPromise(f);
       }
       then(f, r) {
         return wrap(this._promise.then(f, r));
@@ -256,18 +256,19 @@ it('should work with overwritten Promise', async ({ page, server }) => {
       }
     };
     const wrap = p => {
-      const result = new Promise2(() => { }, () => { });
+      const result = new Promise2(() => { });
       result._promise = p;
       return result;
     };
+    //@ts-ignore;
     window.Promise = Promise2;
-    window.__Promise2 = Promise2;
+    window["__Promise2"] = Promise2;
   });
 
   // Sanity check.
   expect(await page.evaluate(() => {
     const p = Promise.all([Promise.race([]), new Promise(() => { }).then(() => { })]);
-    return p instanceof window.__Promise2;
+    return p instanceof window["__Promise2"];
   })).toBe(true);
 
   // Now, the new promise should be awaitable.
@@ -280,16 +281,26 @@ it('should throw when passed more than one parameter', async ({ page, server })
     await f().catch(e => error = e);
     expect('' + error).toContain('Too many arguments');
   }
+  //@ts-ignore
   await expectThrow(() => page.evaluate((a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => page.evaluateHandle((a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => page.$eval('sel', (a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => page.$$eval('sel', (a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => page.evaluate((a, b) => false, 1, 2));
   const frame = page.mainFrame();
+  //@ts-ignore
   await expectThrow(() => frame.evaluate((a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => frame.evaluateHandle((a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => frame.$eval('sel', (a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => frame.$$eval('sel', (a, b) => false, 1, 2));
+  //@ts-ignore
   await expectThrow(() => frame.evaluate((a, b) => false, 1, 2));
 });
 
@@ -325,7 +336,7 @@ it('should return undefined for non-serializable objects', async ({ page, server
 
 it('should fail for circular object', async ({ page, server }) => {
   const result = await page.evaluate(() => {
-    const a = {};
+    const a = {} as any;
     const b = { a };
     a.b = b;
     return a;
@@ -384,12 +395,12 @@ it('should simulate a user gesture', async ({ page, server }) => {
 });
 
 it('should throw a nice error after a navigation', async ({ page, server }) => {
-  const errorPromise = page.evaluate(() => new Promise(f => window.__resolve = f)).catch(e => e);
+  const errorPromise = page.evaluate(() => new Promise(f => window['__resolve'] = f)).catch(e => e) as Promise<Error>;
   await Promise.all([
     page.waitForNavigation(),
     page.evaluate(() => {
       window.location.reload();
-      setTimeout(() => window.__resolve(42), 1000);
+      setTimeout(() => window['__resolve'](42), 1000);
     })
   ]);
   const error = await errorPromise;
@@ -399,7 +410,7 @@ it('should throw a nice error after a navigation', async ({ page, server }) => {
 it('should not throw an error when evaluation does a navigation', async ({ page, server }) => {
   await page.goto(server.PREFIX + '/one-style.html');
   const result = await page.evaluate(() => {
-    window.location = '/empty.html';
+    window.location.href = '/empty.html';
     return [42];
   });
   expect(result).toEqual([42]);
@@ -448,7 +459,7 @@ it.fail(FFOX)('should await promise from popup', async ({ page, server }) => {
   await page.goto(server.EMPTY_PAGE);
   const result = await page.evaluate(() => {
     const win = window.open('about:blank');
-    return new win.Promise(f => f(42));
+    return new win['Promise'](f => f(42));
   });
   expect(result).toBe(42);
 });
@@ -461,7 +472,9 @@ it('should work with new Function() and CSP', async ({ page, server }) => {
 
 it('should work with non-strict expressions', async ({ page, server }) => {
   expect(await page.evaluate(() => {
+    //@ts-ignore
     y = 3.14;
+    //@ts-ignore
     return y;
   })).toBe(3.14);
 });
@@ -469,19 +482,21 @@ it('should work with non-strict expressions', async ({ page, server }) => {
 it('should respect use strict expression', async ({ page, server }) => {
   const error = await page.evaluate(() => {
     "use strict";
+    //@ts-ignore
     variableY = 3.14;
+    //@ts-ignore
     return variableY;
   }).catch(e => e);
   expect(error.message).toContain('variableY');
 });
 
-it('should not leak utility script', async ({ page, server }) => {
+it('should not leak utility script', async function ({ page, server }) {
   expect(await page.evaluate(() => this === window)).toBe(true);
 });
 
 it('should not leak handles', async ({ page, server }) => {
-  const error = await page.evaluate(() => handles.length).catch(e => e);
-  expect(error.message).toContain(' handles');
+  const error = await page.evaluate('handles.length').catch(e => e);
+  expect((error as Error).message).toContain(' handles');
 });
 
 it('should work with CSP', async ({ page, server }) => {
diff --git a/test/page-event-console.spec.js b/test/page-event-console.spec.ts
similarity index 97%
rename from test/page-event-console.spec.js
rename to test/page-event-console.spec.ts
index 474e86b725..6274fb2de7 100644
--- a/test/page-event-console.spec.js
+++ b/test/page-event-console.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should work', async({page, server}) => {
@@ -123,7 +123,7 @@ it('should not throw when there are console messages in detached iframes', async
     page.evaluate(async() => {
       // 1. Create a popup that Playwright is not connected to.
       const win = window.open('');
-      window._popup = win;
+      window["_popup"] = win;
       if (window.document.readyState !== 'complete')
         await new Promise(f => window.addEventListener('load', f));
       // 2. In this popup, create an iframe that console.logs a message.
diff --git a/test/page-event-crash.spec.js b/test/page-event-crash.spec.ts
similarity index 96%
rename from test/page-event-crash.spec.js
rename to test/page-event-crash.spec.ts
index 02c6239082..b7e22227cb 100644
--- a/test/page-event-crash.spec.js
+++ b/test/page-event-crash.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 const CRASH_FAIL = (FFOX && WIN) || USES_HOOKS;
diff --git a/test/page-event-network.spec.js b/test/page-event-network.spec.ts
similarity index 97%
rename from test/page-event-network.spec.js
rename to test/page-event-network.spec.ts
index 8638c923de..f51b8f3d72 100644
--- a/test/page-event-network.spec.js
+++ b/test/page-event-network.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const utils = require('./utils');
+import fs from 'fs';
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, MAC, WIN} = testOptions;
 
 it('Page.Events.Request', async({page, server}) => {
@@ -48,7 +48,7 @@ it('Page.Events.Response', async({page, server}) => {
 it('Page.Events.RequestFailed', async({page, server}) => {
   server.setRoute('/one-style.css', (req, res) => {
     res.setHeader('Content-Type', 'text/css');
-    res.socket.destroy();
+    res.connection.destroy();
   });
   const failedRequests = [];
   page.on('requestfailed', request => failedRequests.push(request));
diff --git a/test/page-event-pageerror.spec.js b/test/page-event-pageerror.spec.ts
similarity index 95%
rename from test/page-event-pageerror.spec.js
rename to test/page-event-pageerror.spec.ts
index d5cb1aa6da..d78ee2dafa 100644
--- a/test/page-event-pageerror.spec.js
+++ b/test/page-event-pageerror.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
+import path from 'path';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should fire', async({page, server}) => {
@@ -26,7 +26,7 @@ it('should fire', async({page, server}) => {
   ]);
   expect(error.name).toBe('Error');
   expect(error.message).toBe('Fancy error!');
-  let stack = await page.evaluate(() => window.e.stack);
+  let stack = await page.evaluate(() => window['e'].stack);
   // Note that WebKit reports the stack of the 'throw' statement instead of the Error constructor call.
   if (WEBKIT)
     stack = stack.replace('14:25', '15:19');
diff --git a/test/page-event-popup.spec.js b/test/page-event-popup.spec.ts
similarity index 91%
rename from test/page-event-popup.spec.js
rename to test/page-event-popup.spec.ts
index 584c1ca908..867a0021cd 100644
--- a/test/page-event-popup.spec.js
+++ b/test/page-event-popup.spec.ts
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT, MAC} = testOptions;
 
@@ -22,7 +22,7 @@ it('should work', async({browser}) => {
   const page = await context.newPage();
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(() => window.__popup = window.open('about:blank')),
+    page.evaluate(() => window["__popup"] = window.open('about:blank')),
   ]);
   expect(await page.evaluate(() => !!window.opener)).toBe(false);
   expect(await popup.evaluate(() => !!window.opener)).toBe(true);
@@ -35,7 +35,7 @@ it('should work with window features', async({browser, server}) => {
   await page.goto(server.EMPTY_PAGE);
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(() => window.__popup = window.open(window.location.href, 'Title', 'toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=yes,width=780,height=200,top=0,left=0')),
+    page.evaluate(() => window["__popup"] = window.open(window.location.href, 'Title', 'toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=yes,width=780,height=200,top=0,left=0')),
   ]);
   expect(await page.evaluate(() => !!window.opener)).toBe(false);
   expect(await popup.evaluate(() => !!window.opener)).toBe(true);
@@ -91,7 +91,7 @@ it('should work with empty url', async({browser}) => {
   const page = await context.newPage();
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(() => window.__popup = window.open('')),
+    page.evaluate(() => window["__popup"] = window.open('')),
   ]);
   expect(await page.evaluate(() => !!window.opener)).toBe(false);
   expect(await popup.evaluate(() => !!window.opener)).toBe(true);
@@ -103,7 +103,7 @@ it('should work with noopener and no url', async({browser}) => {
   const page = await context.newPage();
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(() => window.__popup = window.open(undefined, null, 'noopener')),
+    page.evaluate(() => window["__popup"] = window.open(undefined, null, 'noopener')),
   ]);
   // Chromium reports `about:blank#blocked` here.
   expect(popup.url().split('#')[0]).toBe('about:blank');
@@ -117,7 +117,7 @@ it('should work with noopener and about:blank', async({browser}) => {
   const page = await context.newPage();
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(() => window.__popup = window.open('about:blank', null, 'noopener')),
+    page.evaluate(() => window["__popup"] = window.open('about:blank', null, 'noopener')),
   ]);
   expect(await page.evaluate(() => !!window.opener)).toBe(false);
   expect(await popup.evaluate(() => !!window.opener)).toBe(false);
@@ -130,7 +130,7 @@ it('should work with noopener and url', async({browser, server}) => {
   await page.goto(server.EMPTY_PAGE);
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(url => window.__popup = window.open(url, null, 'noopener'), server.EMPTY_PAGE),
+    page.evaluate(url => window["__popup"] = window.open(url, null, 'noopener'), server.EMPTY_PAGE),
   ]);
   expect(await page.evaluate(() => !!window.opener)).toBe(false);
   expect(await popup.evaluate(() => !!window.opener)).toBe(false);
diff --git a/test/page-event-request.spec.js b/test/page-event-request.spec.ts
similarity index 90%
rename from test/page-event-request.spec.js
rename to test/page-event-request.spec.ts
index 9391509344..d4ed1ef115 100644
--- a/test/page-event-request.spec.js
+++ b/test/page-event-request.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const utils = require('./utils');
+import fs from 'fs';
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, MAC, WIN} = testOptions;
 
 it('should fire for navigation requests', async({page, server}) => {
@@ -46,9 +46,9 @@ it('should fire for fetches', async({page, server}) => {
 
 it('should report requests and responses handled by service worker', async({page, server}) => {
   await page.goto(server.PREFIX + '/serviceworkers/fetchdummy/sw.html');
-  await page.evaluate(() => window.activationPromise);
+  await page.evaluate(() => window["activationPromise"]);
   const [swResponse, request] = await Promise.all([
-    page.evaluate(() => fetchDummy('foo')),
+    page.evaluate(() => window["fetchDummy"]('foo')),
     page.waitForEvent('request'),
   ]);
   expect(swResponse).toBe('responseFromServiceWorker:foo');
diff --git a/test/page-expose-function.spec.js b/test/page-expose-function.spec.ts
similarity index 86%
rename from test/page-expose-function.spec.js
rename to test/page-expose-function.spec.ts
index 94135c3aff..9e6b6b1dcc 100644
--- a/test/page-expose-function.spec.js
+++ b/test/page-expose-function.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('exposeBinding should work', async({browser}) => {
@@ -30,7 +30,7 @@ it('exposeBinding should work', async({browser}) => {
     return a + b;
   });
   const result = await page.evaluate(async function() {
-    return add(5, 6);
+    return window['add'](5, 6);
   });
   expect(bindingSource.context).toBe(context);
   expect(bindingSource.page).toBe(page);
@@ -44,23 +44,23 @@ it('should work', async({page, server}) => {
     return a * b;
   });
   const result = await page.evaluate(async function() {
-    return await compute(9, 4);
+    return await window['compute'](9, 4);
   });
   expect(result).toBe(36);
 });
 
 it('should work with handles and complex objects', async({page, server}) => {
   const fooHandle = await page.evaluateHandle(() => {
-    window.fooValue = { bar: 2 };
-    return window.fooValue;
+    window['fooValue'] = { bar: 2 };
+    return window['fooValue'];
   });
   await page.exposeFunction('handle', () => {
     return [{ foo: fooHandle }];
   });
   const equals = await page.evaluate(async function() {
-    const value = await handle();
+    const value = await window['handle']();
     const [{ foo }] = value;
-    return foo === window.fooValue;
+    return foo === window['fooValue'];
   });
   expect(equals).toBe(true);
 });
@@ -71,7 +71,7 @@ it('should throw exception in page context', async({page, server}) => {
   });
   const {message, stack} = await page.evaluate(async() => {
     try {
-      await woof();
+      await window["woof"]();
     } catch (e) {
       return {message: e.message, stack: e.stack};
     }
@@ -86,7 +86,7 @@ it('should support throwing "null"', async({page, server}) => {
   });
   const thrown = await page.evaluate(async() => {
     try {
-      await woof();
+      await window["woof"]();
     } catch (e) {
       return e;
     }
@@ -99,7 +99,7 @@ it('should be callable from-inside addInitScript', async({page, server}) => {
   await page.exposeFunction('woof', function() {
     called = true;
   });
-  await page.addInitScript(() => woof());
+  await page.addInitScript(() => window["woof"]());
   await page.reload();
   expect(called).toBe(true);
 });
@@ -111,7 +111,7 @@ it('should survive navigation', async({page, server}) => {
 
   await page.goto(server.EMPTY_PAGE);
   const result = await page.evaluate(async function() {
-    return await compute(9, 4);
+    return await window['compute'](9, 4);
   });
   expect(result).toBe(36);
 });
@@ -122,7 +122,7 @@ it('should await returned promise', async({page, server}) => {
   });
 
   const result = await page.evaluate(async function() {
-    return await compute(3, 5);
+    return await window['compute'](3, 5);
   });
   expect(result).toBe(15);
 });
@@ -135,7 +135,7 @@ it('should work on frames', async({page, server}) => {
   await page.goto(server.PREFIX + '/frames/nested-frames.html');
   const frame = page.frames()[1];
   const result = await frame.evaluate(async function() {
-    return await compute(3, 5);
+    return await window['compute'](3, 5);
   });
   expect(result).toBe(15);
 });
@@ -148,7 +148,7 @@ it('should work on frames before navigation', async({page, server}) => {
 
   const frame = page.frames()[1];
   const result = await frame.evaluate(async function() {
-    return await compute(3, 5);
+    return await window['compute'](3, 5);
   });
   expect(result).toBe(15);
 });
@@ -161,7 +161,7 @@ it('should work after cross origin navigation', async({page, server}) => {
 
   await page.goto(server.CROSS_PROCESS_PREFIX + '/empty.html');
   const result = await page.evaluate(async function() {
-    return await compute(9, 4);
+    return await window['compute'](9, 4);
   });
   expect(result).toBe(36);
 });
@@ -170,6 +170,6 @@ it('should work with complex objects', async({page, server}) => {
   await page.exposeFunction('complexObject', function(a, b) {
     return {x: a.x + b.x};
   });
-  const result = await page.evaluate(async() => complexObject({x: 5}, {x: 2}));
+  const result = await page.evaluate(async() => window['complexObject']({x: 5}, {x: 2}));
   expect(result.x).toBe(7);
 });
diff --git a/test/page-fill.spec.js b/test/page-fill.spec.ts
similarity index 86%
rename from test/page-fill.spec.js
rename to test/page-fill.spec.ts
index ab9c390ce1..80c353eb04 100644
--- a/test/page-fill.spec.js
+++ b/test/page-fill.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 async function giveItAChanceToFill(page) {
@@ -29,13 +29,13 @@ async function giveItAChanceToFill(page) {
 it('should fill textarea', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/textarea.html');
   await page.fill('textarea', 'some value');
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
 });
 
 it('should fill input', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/textarea.html');
   await page.fill('input', 'some value');
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
 });
 
 it('should throw on unsupported inputs', async({page, server}) => {
@@ -53,7 +53,7 @@ it('should fill different input types', async({page, server}) => {
   for (const type of ['password', 'search', 'tel', 'text', 'url']) {
     await page.$eval('input', (input, type) => input.setAttribute('type', type), type);
     await page.fill('input', 'text ' + type);
-    expect(await page.evaluate(() => result)).toBe('text ' + type);
+    expect(await page.evaluate(() => window['result'])).toBe('text ' + type);
   }
 });
 
@@ -105,14 +105,14 @@ it('should fill elements with existing value and selection', async({page, server
 
   await page.$eval('input', input => input.value = 'value one');
   await page.fill('input', 'another value');
-  expect(await page.evaluate(() => result)).toBe('another value');
+  expect(await page.evaluate(() => window['result'])).toBe('another value');
 
   await page.$eval('input', input => {
     input.selectionStart = 1;
     input.selectionEnd = 2;
   });
   await page.fill('input', 'maybe this one');
-  expect(await page.evaluate(() => result)).toBe('maybe this one');
+  expect(await page.evaluate(() => window['result'])).toBe('maybe this one');
 
   await page.$eval('div[contenteditable]', div => {
     div.innerHTML = 'some text <span>some more text<span> and even more text';
@@ -136,7 +136,7 @@ it('should throw when element is not an <input>, <textarea> or [contenteditable]
 it('should throw if passed a non-string value', async({page, server}) => {
   let error = null;
   await page.goto(server.PREFIX + '/input/textarea.html');
-  await page.fill('textarea', 123).catch(e => error = e);
+  await page.fill('textarea', 123 as any).catch(e => error = e);
   expect(error.message).toContain('value: expected string, got number');
 });
 
@@ -148,11 +148,11 @@ it('should retry on disabled element', async({page, server}) => {
   const promise = page.fill('input', 'some value').then(() => done = true);
   await giveItAChanceToFill(page);
   expect(done).toBe(false);
-  expect(await page.evaluate(() => result)).toBe('');
+  expect(await page.evaluate(() => window['result'])).toBe('');
 
   await page.$eval('input', i => i.disabled = false);
   await promise;
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
 });
 
 it('should retry on readonly element', async({page, server}) => {
@@ -163,11 +163,11 @@ it('should retry on readonly element', async({page, server}) => {
   const promise = page.fill('textarea', 'some value').then(() => done = true);
   await giveItAChanceToFill(page);
   expect(done).toBe(false);
-  expect(await page.evaluate(() => result)).toBe('');
+  expect(await page.evaluate(() => window['result'])).toBe('');
 
   await page.$eval('textarea', i => i.readOnly = false);
   await promise;
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
 });
 
 it('should retry on invisible element', async({page, server}) => {
@@ -178,11 +178,11 @@ it('should retry on invisible element', async({page, server}) => {
   const promise = page.fill('input', 'some value').then(() => done = true);
   await giveItAChanceToFill(page);
   expect(done).toBe(false);
-  expect(await page.evaluate(() => result)).toBe('');
+  expect(await page.evaluate(() => window['result'])).toBe('');
 
   await page.$eval('input', i => i.style.display = 'inline');
   await promise;
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
 });
 
 it('should be able to fill the body', async({page}) => {
@@ -210,19 +210,19 @@ it('should be able to fill when focus is in the wrong frame', async({page}) => {
 it('should be able to fill the input[type=number]', async({page}) => {
   await page.setContent(`<input id="input" type="number"></input>`);
   await page.fill('input', '42');
-  expect(await page.evaluate(() => input.value)).toBe('42');
+  expect(await page.evaluate(() => window['input'].value)).toBe('42');
 });
 
 it('should be able to fill exponent into the input[type=number]', async({page}) => {
   await page.setContent(`<input id="input" type="number"></input>`);
   await page.fill('input', '-10e5');
-  expect(await page.evaluate(() => input.value)).toBe('-10e5');
+  expect(await page.evaluate(() => window['input'].value)).toBe('-10e5');
 });
 
 it('should be able to fill input[type=number] with empty string', async({page}) => {
   await page.setContent(`<input id="input" type="number" value="123"></input>`);
   await page.fill('input', '');
-  expect(await page.evaluate(() => input.value)).toBe('');
+  expect(await page.evaluate(() => window['input'].value)).toBe('');
 });
 
 it('should not be able to fill text into the input[type=number]', async({page}) => {
@@ -235,7 +235,7 @@ it('should not be able to fill text into the input[type=number]', async({page})
 it('should be able to clear', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/textarea.html');
   await page.fill('input', 'some value');
-  expect(await page.evaluate(() => result)).toBe('some value');
+  expect(await page.evaluate(() => window['result'])).toBe('some value');
   await page.fill('input', '');
-  expect(await page.evaluate(() => result)).toBe('');
+  expect(await page.evaluate(() => window['result'])).toBe('');
 });
diff --git a/test/page-goto.spec.js b/test/page-goto.spec.ts
similarity index 97%
rename from test/page-goto.spec.js
rename to test/page-goto.spec.ts
index 68e059e5c9..c0810126ed 100644
--- a/test/page-goto.spec.js
+++ b/test/page-goto.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
-const path = require('path');
-const url = require('url');
+import utils from './utils';
+import path from 'path';
+import url from 'url';
 const {FFOX, CHROMIUM, WEBKIT, ASSETS_DIR, MAC, WIN} = testOptions;
 
 it('should work', async({page, server}) => {
@@ -192,12 +192,12 @@ it('should not crash when navigating to bad SSL after a cross origin navigation'
 
 it('should not throw if networkidle0 is passed as an option', async({page, server}) => {
   let error = null;
-  await page.goto(server.EMPTY_PAGE, {waitUntil: 'networkidle0'});
+  await page.goto(server.EMPTY_PAGE, {waitUntil: 'networkidle0' as any});
 });
 
 it('should throw if networkidle2 is passed as an option', async({page, server}) => {
   let error = null;
-  await page.goto(server.EMPTY_PAGE, {waitUntil: 'networkidle2'}).catch(err => error = err);
+  await page.goto(server.EMPTY_PAGE, {waitUntil: 'networkidle2' as any}).catch(err => error = err);
   expect(error.message).toContain(`waitUntil: expected one of (load|domcontentloaded|networkidle)`);
 });
 
@@ -338,7 +338,7 @@ it('should not leak listeners during navigation', async({page, server}) => {
   process.on('warning', warningHandler);
   for (let i = 0; i < 20; ++i)
     await page.goto(server.EMPTY_PAGE);
-  process.removeListener('warning', warningHandler);
+  process.off('warning', warningHandler);
   expect(warning).toBe(null);
 });
 
@@ -348,7 +348,7 @@ it('should not leak listeners during bad navigation', async({page, server}) => {
   process.on('warning', warningHandler);
   for (let i = 0; i < 20; ++i)
     await page.goto('asdf').catch(e => {/* swallow navigation error */});
-  process.removeListener('warning', warningHandler);
+  process.off('warning', warningHandler);
   expect(warning).toBe(null);
 });
 
@@ -359,7 +359,7 @@ it('should not leak listeners during navigation of 20 pages', async({page, conte
   const pages = await Promise.all([...Array(20)].map(() => context.newPage()));
   await Promise.all(pages.map(page => page.goto(server.EMPTY_PAGE)));
   await Promise.all(pages.map(page => page.close()));
-  process.removeListener('warning', warningHandler);
+  process.off('warning', warningHandler);
   expect(warning).toBe(null);
 });
 
@@ -370,7 +370,7 @@ it('should not leak listeners during 20 waitForNavigation', async({page, context
   const promises = [...Array(20)].map(() => page.waitForNavigation());
   await page.goto(server.EMPTY_PAGE);
   await Promise.all(promises);
-  process.removeListener('warning', warningHandler);
+  process.off('warning', warningHandler);
   expect(warning).toBe(null);
 });
 
@@ -412,7 +412,7 @@ it('should fail when navigating and show the url at the error message', async fu
 
 it('should be able to navigate to a page controlled by service worker', async({page, server}) => {
   await page.goto(server.PREFIX + '/serviceworkers/fetch/sw.html');
-  await page.evaluate(() => window.activationPromise);
+  await page.evaluate(() => window["activationPromise"]);
   await page.goto(server.PREFIX + '/serviceworkers/fetch/sw.html');
 });
 
diff --git a/test/page-history.spec.js b/test/page-history.spec.ts
similarity index 94%
rename from test/page-history.spec.js
rename to test/page-history.spec.ts
index d115bc0ff7..5391f83117 100644
--- a/test/page-history.spec.js
+++ b/test/page-history.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const url = require('url');
+import path from 'path';
+import url from 'url';
 const {FFOX, CHROMIUM, WEBKIT, ASSETS_DIR, MAC, WIN} = testOptions;
 
 it('page.goBack should work', async({page, server}) => {
@@ -81,9 +81,9 @@ it.fail(WEBKIT && MAC)('page.goBack should work for file urls', async ({page, se
 
 it('page.reload should work', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
-  await page.evaluate(() => window._foo = 10);
+  await page.evaluate(() => window["_foo"] = 10);
   await page.reload();
-  expect(await page.evaluate(() => window._foo)).toBe(undefined);
+  expect(await page.evaluate(() => window["_foo"])).toBe(undefined);
 });
 
 it('page.reload should work with data url', async({page, server}) => {
diff --git a/test/page-network-idle.spec.js b/test/page-network-idle.spec.ts
similarity index 90%
rename from test/page-network-idle.spec.js
rename to test/page-network-idle.spec.ts
index 71c06b19c3..dc6be78cce 100644
--- a/test/page-network-idle.spec.js
+++ b/test/page-network-idle.spec.ts
@@ -14,11 +14,13 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
-const path = require('path');
-const url = require('url');
+import utils from './utils';
+import path from 'path';
+import url from 'url';
+import { Frame, Page } from '..';
+import { TestServer } from '../utils/testserver';
 const {FFOX, CHROMIUM, WEBKIT, ASSETS_DIR, MAC, WIN} = testOptions;
 
 it('should navigate to empty page with networkidle', async({page, server}) => {
@@ -26,13 +28,7 @@ it('should navigate to empty page with networkidle', async({page, server}) => {
   expect(response.status()).toBe(200);
 });
 
-/**
- * @param {import('../index').Frame} frame
- * @param {TestServer} server
- * @param {() => Promise<void>} action
- * @param {boolean} isSetContent
- */
-async function networkIdleTest(frame, server, action, isSetContent) {
+async function networkIdleTest(frame: Frame, server: TestServer, action: () => Promise<any>, isSetContent?: boolean) {
   const finishResponse = response => {
     response.statusCode = 404;
     response.end(`File not found`);
@@ -40,14 +36,14 @@ async function networkIdleTest(frame, server, action, isSetContent) {
   const waitForRequest = suffix => {
     return Promise.all([
       server.waitForRequest(suffix),
-      frame._page.waitForRequest(server.PREFIX + suffix),
+      (frame['_page'] as Page).waitForRequest(server.PREFIX + suffix),
     ]);
   }
   let responses = {};
   // Hold on to a bunch of requests without answering.
-  server.setRoute('/fetch-request-a.js', (req, res) => responses.a = res);
+  server.setRoute('/fetch-request-a.js', (req, res) => responses['a'] = res);
   const firstFetchResourceRequested = waitForRequest('/fetch-request-a.js');
-  server.setRoute('/fetch-request-d.js', (req, res) => responses.d = res);
+  server.setRoute('/fetch-request-d.js', (req, res) => responses['d'] = res);
   const secondFetchResourceRequested = waitForRequest('/fetch-request-d.js');
 
   const waitForLoadPromise = isSetContent ? Promise.resolve() : frame.waitForNavigation({ waitUntil: 'load' });
@@ -68,18 +64,18 @@ async function networkIdleTest(frame, server, action, isSetContent) {
   await firstFetchResourceRequested;
   expect(actionFinished).toBe(false);
 
-  expect(responses.a).toBeTruthy();
+  expect(responses['a']).toBeTruthy();
   let timer;
   let timerTriggered = false;
   // Finishing response should trigger the second round.
-  finishResponse(responses.a);
+  finishResponse(responses['a']);
 
   // Wait for the second round to be requested.
   await secondFetchResourceRequested;
   expect(actionFinished).toBe(false);
   // Finishing the last response should trigger networkidle.
   timer = setTimeout(() => timerTriggered = true, 500);
-  finishResponse(responses.d);
+  finishResponse(responses['d']);
 
   const response = await actionPromise;
   clearTimeout(timer);
diff --git a/test/page-route.spec.js b/test/page-route.spec.ts
similarity index 99%
rename from test/page-route.spec.js
rename to test/page-route.spec.ts
index c410c86e6b..edff4714be 100644
--- a/test/page-route.spec.js
+++ b/test/page-route.spec.ts
@@ -14,12 +14,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const { helper } = require('../lib/helper');
-const vm = require('vm');
+import fs from 'fs';
+import path from 'path';
+import { helper } from '../lib/helper';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, HEADLESS} = testOptions;
 
 it('should intercept', async({page, server}) => {
diff --git a/test/page-screenshot.spec.js b/test/page-screenshot.spec.ts
similarity index 99%
rename from test/page-screenshot.spec.js
rename to test/page-screenshot.spec.ts
index e01247bf78..8951c0f3a8 100644
--- a/test/page-screenshot.spec.js
+++ b/test/page-screenshot.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, USES_HOOKS, HEADLESS} = testOptions;
-const {PNG} = require('pngjs');
+import {PNG} from 'pngjs';
 
 // Firefox headful produces a different image.
 const ffheadful = FFOX && !HEADLESS;
diff --git a/test/page-select-option.spec.js b/test/page-select-option.spec.ts
similarity index 73%
rename from test/page-select-option.spec.js
rename to test/page-select-option.spec.ts
index ed4a3c3233..94c5db4709 100644
--- a/test/page-select-option.spec.js
+++ b/test/page-select-option.spec.ts
@@ -14,53 +14,53 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should select single option', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
   await page.selectOption('select', 'blue');
-  expect(await page.evaluate(() => result.onInput)).toEqual(['blue']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['blue']);
 });
 
 it('should select single option by value', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
   await page.selectOption('select', { value: 'blue' });
-  expect(await page.evaluate(() => result.onInput)).toEqual(['blue']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['blue']);
 });
 
 it('should select single option by label', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
   await page.selectOption('select', { label: 'Indigo' });
-  expect(await page.evaluate(() => result.onInput)).toEqual(['indigo']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['indigo']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['indigo']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['indigo']);
 });
 
 it('should select single option by handle', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
   await page.selectOption('select', await page.$('[id=whiteOption]'));
-  expect(await page.evaluate(() => result.onInput)).toEqual(['white']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['white']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['white']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['white']);
 });
 
 it('should select single option by index', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
   await page.selectOption('select', { index: 2 });
-  expect(await page.evaluate(() => result.onInput)).toEqual(['brown']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['brown']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['brown']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['brown']);
 });
 
 it('should select single option by multiple attributes', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
   await page.selectOption('select', { value: 'green', label: 'Green' });
-  expect(await page.evaluate(() => result.onInput)).toEqual(['green']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['green']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['green']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['green']);
 });
 
 it('should not select single option when some attributes do not match', async({page, server}) => {
@@ -71,13 +71,13 @@ it('should not select single option when some attributes do not match', async({p
 
 it('should select only first option', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
-  await page.selectOption('select', 'blue', 'green', 'red');
-  expect(await page.evaluate(() => result.onInput)).toEqual(['blue']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['blue']);
+  await page.selectOption('select', ['blue', 'green', 'red']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['blue']);
 });
 
 it('should not throw when select causes navigation', async({page, server}) => { await page.goto(server.PREFIX + '/input/select.html');
-  await page.$eval('select', select => select.addEventListener('input', () => window.location = '/empty.html'));
+  await page.$eval('select', select => select.addEventListener('input', () => window.location.href = '/empty.html'));
   await Promise.all([
     page.selectOption('select', 'blue'),
     page.waitForNavigation(),
@@ -87,25 +87,25 @@ it('should not throw when select causes navigation', async({page, server}) => {
 
 it('should select multiple options', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
-  await page.evaluate(() => makeMultiple());
+  await page.evaluate(() => window['makeMultiple']());
   await page.selectOption('select', ['blue', 'green', 'red']);
-  expect(await page.evaluate(() => result.onInput)).toEqual(['blue', 'green', 'red']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['blue', 'green', 'red']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['blue', 'green', 'red']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['blue', 'green', 'red']);
 });
 
 it('should select multiple options with attributes', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
-  await page.evaluate(() => makeMultiple());
+  await page.evaluate(() => window['makeMultiple']());
   await page.selectOption('select', [{ value: 'blue' }, { label: 'Green' }, { index: 4 }]);
-  expect(await page.evaluate(() => result.onInput)).toEqual(['blue', 'gray', 'green']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['blue', 'gray', 'green']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['blue', 'gray', 'green']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['blue', 'gray', 'green']);
 });
 
 it('should respect event bubbling', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
   await page.selectOption('select', 'blue');
-  expect(await page.evaluate(() => result.onBubblingInput)).toEqual(['blue']);
-  expect(await page.evaluate(() => result.onBubblingChange)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onBubblingInput)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onBubblingChange)).toEqual(['blue']);
 });
 
 it('should throw when element is not a <select>', async({page, server}) => {
@@ -123,7 +123,7 @@ it('should return [] on no matched values', async({page, server}) => {
 
 it('should return an array of matched values', async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
-  await page.evaluate(() => makeMultiple());
+  await page.evaluate(() => window['makeMultiple']());
   const result = await page.selectOption('select', ['blue','black','magenta']);
   expect(result.reduce((accumulator,current) => ['blue', 'black', 'magenta'].includes(current) && accumulator, true)).toEqual(true);
 });
@@ -142,7 +142,7 @@ it('should return [] on no values',async({page, server}) => {
 
 it('should not allow null items',async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
-  await page.evaluate(() => makeMultiple());
+  await page.evaluate(() => window['makeMultiple']());
   let error = null
   await page.selectOption('select', ['blue', null, 'black','magenta']).catch(e => error = e);
   expect(error.message).toContain('options[1]: expected object, got null');
@@ -150,7 +150,7 @@ it('should not allow null items',async({page, server}) => {
 
 it('should unselect with null',async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
-  await page.evaluate(() => makeMultiple());
+  await page.evaluate(() => window['makeMultiple']());
   const result = await page.selectOption('select', ['blue', 'black','magenta']);
   expect(result.reduce((accumulator,current) => ['blue', 'black', 'magenta'].includes(current) && accumulator, true)).toEqual(true);
   await page.selectOption('select', null);
@@ -159,7 +159,7 @@ it('should unselect with null',async({page, server}) => {
 
 it('should deselect all options when passed no values for a multiple select',async({page, server}) => {
   await page.goto(server.PREFIX + '/input/select.html');
-  await page.evaluate(() => makeMultiple());
+  await page.evaluate(() => window['makeMultiple']());
   await page.selectOption('select', ['blue','black','magenta']);
   await page.selectOption('select', []);
   expect(await page.$eval('select', select => Array.from(select.options).every(option => !option.selected))).toEqual(true);
@@ -178,7 +178,7 @@ it('should throw if passed wrong types', async({page, server}) => {
 
   error = null;
   try {
-    await page.selectOption('select', 12);
+    await page.selectOption('select', 12 as any);
   } catch (e) {
     error = e;
   }
@@ -186,7 +186,7 @@ it('should throw if passed wrong types', async({page, server}) => {
 
   error = null;
   try {
-    await page.selectOption('select', { value: 12 });
+    await page.selectOption('select', { value: 12 } as any);
   } catch (e) {
     error = e;
   }
@@ -194,7 +194,7 @@ it('should throw if passed wrong types', async({page, server}) => {
 
   error = null;
   try {
-    await page.selectOption('select', { label: 12 });
+    await page.selectOption('select', { label: 12 } as any);
   } catch (e) {
     error = e;
   }
@@ -202,7 +202,7 @@ it('should throw if passed wrong types', async({page, server}) => {
 
   error = null;
   try {
-    await page.selectOption('select', { index: '12' });
+    await page.selectOption('select', { index: '12' } as any);
   } catch (e) {
     error = e;
   }
@@ -213,6 +213,6 @@ it('should work when re-defining top-level Event class', async({page, server}) =
   await page.goto(server.PREFIX + '/input/select.html');
   await page.evaluate(() => window.Event = null);
   await page.selectOption('select', 'blue');
-  expect(await page.evaluate(() => result.onInput)).toEqual(['blue']);
-  expect(await page.evaluate(() => result.onChange)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onInput)).toEqual(['blue']);
+  expect(await page.evaluate(() => window['result'].onChange)).toEqual(['blue']);
 });
diff --git a/test/page-set-content.spec.js b/test/page-set-content.spec.ts
similarity index 97%
rename from test/page-set-content.spec.js
rename to test/page-set-content.spec.ts
index a80e08b370..382e2fdb90 100644
--- a/test/page-set-content.spec.js
+++ b/test/page-set-content.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 const expectedOutput = '<html><head></head><body><div>hello</div></body></html>';
diff --git a/test/page-set-extra-http-headers.spec.js b/test/page-set-extra-http-headers.spec.ts
similarity index 93%
rename from test/page-set-extra-http-headers.spec.js
rename to test/page-set-extra-http-headers.spec.ts
index 5d98b33c4e..8ebe27cc9e 100644
--- a/test/page-set-extra-http-headers.spec.js
+++ b/test/page-set-extra-http-headers.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const utils = require('./utils');
+import fs from 'fs';
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, MAC, WIN} = testOptions;
 
 
@@ -79,7 +79,7 @@ it('should override extra headers from browser context', async({browser, server}
 it('should throw for non-string header values', async({page, server}) => {
   let error = null;
   try {
-    await page.setExtraHTTPHeaders({ 'foo': 1 });
+    await page.setExtraHTTPHeaders({ 'foo': 1 as any });
   } catch (e) {
     error = e;
   }
diff --git a/test/page-set-input-files.spec.js b/test/page-set-input-files.spec.ts
similarity index 98%
rename from test/page-set-input-files.spec.js
rename to test/page-set-input-files.spec.ts
index c1e8eb6b8e..440ec69676 100644
--- a/test/page-set-input-files.spec.js
+++ b/test/page-set-input-files.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const fs = require('fs');
-const formidable = require('formidable');
+import path from 'path';
+import fs from 'fs';
+import formidable from 'formidable';
 
 const FILE_TO_UPLOAD = path.join(__dirname, '/assets/file-to-upload.txt');
 
diff --git a/test/page-wait-for-load-state.spec.js b/test/page-wait-for-load-state.spec.ts
similarity index 91%
rename from test/page-wait-for-load-state.spec.js
rename to test/page-wait-for-load-state.spec.ts
index 9e05a42c6b..0b9cb2fb27 100644
--- a/test/page-wait-for-load-state.spec.js
+++ b/test/page-wait-for-load-state.spec.ts
@@ -14,11 +14,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
-const path = require('path');
-const url = require('url');
+import utils from './utils';
+import path from 'path';
+import url from 'url';
+import { Route } from '..';
 const {FFOX, CHROMIUM, WEBKIT, ASSETS_DIR, MAC, WIN} = testOptions;
 
 it('should pick up ongoing navigation', async({page, server}) => {
@@ -35,7 +36,7 @@ it('should pick up ongoing navigation', async({page, server}) => {
 });
 
 it('should respect timeout', async({page, server}) => {
-  server.setRoute('/one-style.css', (req, res) => response = res);
+  server.setRoute('/one-style.css', (req, res) => void 0);
   await page.goto(server.PREFIX + '/one-style.html', {waitUntil: 'domcontentloaded'});
   const error = await page.waitForLoadState('load', { timeout: 1 }).catch(e => e);
   expect(error.message).toContain('page.waitForLoadState: Timeout 1ms exceeded.');
@@ -48,13 +49,13 @@ it('should resolve immediately if loaded', async({page, server}) => {
 
 it('should throw for bad state', async({page, server}) => {
   await page.goto(server.PREFIX + '/one-style.html');
-  const error = await page.waitForLoadState('bad').catch(e => e);
+  const error = await page.waitForLoadState('bad' as any).catch(e => e);
   expect(error.message).toContain(`state: expected one of (load|domcontentloaded|networkidle)`);
 });
 
 it('should resolve immediately if load state matches', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
-  server.setRoute('/one-style.css', (req, res) => response = res);
+  server.setRoute('/one-style.css', (req, res) => void 0);
   await page.goto(server.PREFIX + '/one-style.html', {waitUntil: 'domcontentloaded'});
   await page.waitForLoadState('domcontentloaded');
 });
@@ -63,7 +64,7 @@ it('should work with pages that have loaded before being connected to', async({p
   await page.goto(server.EMPTY_PAGE);
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(() => window._popup = window.open(document.location.href)),
+    page.evaluate(() => window["_popup"] = window.open(document.location.href)),
   ]);
   // The url is about:blank in FF.
   // expect(popup.url()).toBe(server.EMPTY_PAGE);
@@ -152,7 +153,7 @@ it('should resolve after popup load', async({browser, server}) => {
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
     server.waitForRequest('/one-style.css'),
-    page.evaluate(url => window.popup = window.open(url), server.PREFIX + '/one-style.html'),
+    page.evaluate(url => window["popup"] = window.open(url), server.PREFIX + '/one-style.html'),
   ]);
   let resolved = false;
   const loadSatePromise = popup.waitForLoadState().then(() => resolved = true);
@@ -171,7 +172,7 @@ it('should work for frame', async({page, server}) => {
   await page.goto(server.PREFIX + '/frames/one-frame.html');
   const frame = page.frames()[1];
 
-  const requestPromise = new Promise(resolve => page.route(server.PREFIX + '/one-style.css',resolve));
+  const requestPromise = new Promise<Route>(resolve => page.route(server.PREFIX + '/one-style.css',resolve));
   await frame.goto(server.PREFIX + '/one-style.html', {waitUntil: 'domcontentloaded'});
   const request = await requestPromise;
   let resolved = false;
diff --git a/test/page-wait-for-navigation.spec.js b/test/page-wait-for-navigation.spec.ts
similarity index 97%
rename from test/page-wait-for-navigation.spec.js
rename to test/page-wait-for-navigation.spec.ts
index 49ccd1b80c..dad58352dc 100644
--- a/test/page-wait-for-navigation.spec.js
+++ b/test/page-wait-for-navigation.spec.ts
@@ -14,11 +14,13 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
+
+import utils from './utils';
+import path from 'path';
+import url from 'url';
+import { Frame } from '..';
 
-const utils = require('./utils');
-const path = require('path');
-const url = require('url');
 const {FFOX, CHROMIUM, WEBKIT, ASSETS_DIR, MAC, WIN} = testOptions;
 
 it('should work', async({page, server}) => {
@@ -145,7 +147,7 @@ it('should work with DOM history.back()/history.forward()', async({page, server}
 it.fail(FFOX)('should work when subframe issues window.stop()', async({page, server}) => {
   server.setRoute('/frames/style.css', (req, res) => {});
   const navigationPromise = page.goto(server.PREFIX + '/frames/one-frame.html');
-  const frame = await new Promise(f => page.once('frameattached', f));
+  const frame = await new Promise<Frame>(f => page.once('frameattached', f));
   await new Promise(fulfill => page.on('framenavigated', f => {
     if (f === frame)
       fulfill();
@@ -243,7 +245,7 @@ it('should fail when frame detaches', async({page, server}) => {
   let error = null;
   await Promise.all([
     frame.waitForNavigation().catch(e => error = e),
-    frame.evaluate('window.location = "/empty.html"'),
+    frame.evaluate('window.location.href = "/empty.html"'),
     page.evaluate('setTimeout(() => document.querySelector("iframe").remove())'),
   ]).catch(e => error = e);
   expect(error.message).toContain('waiting for navigation until "load"');
diff --git a/test/page-wait-for-request.spec.js b/test/page-wait-for-request.spec.ts
similarity index 96%
rename from test/page-wait-for-request.spec.js
rename to test/page-wait-for-request.spec.ts
index 59cd49a914..46297ed53b 100644
--- a/test/page-wait-for-request.spec.js
+++ b/test/page-wait-for-request.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should work', async({page, server}) => {
diff --git a/test/page-wait-for-response.spec.js b/test/page-wait-for-response.spec.ts
similarity index 91%
rename from test/page-wait-for-response.spec.js
rename to test/page-wait-for-response.spec.ts
index c3ece05d50..6eb62b04e1 100644
--- a/test/page-wait-for-response.spec.js
+++ b/test/page-wait-for-response.spec.ts
@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const util = require('util');
-const vm = require('vm');
+import path from 'path';
+import util from 'util';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
 it('should work', async({page, server}) => {
@@ -50,7 +50,7 @@ it('should respect default timeout', async({page, playwright}) => {
 it('should work with predicate', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   const [response] = await Promise.all([
-    page.waitForEvent('response', response => response.url() === server.PREFIX + '/digits/2.png'),
+    page.waitForEvent('request', response => response.url() === server.PREFIX + '/digits/2.png'),
     page.evaluate(() => {
       fetch('/digits/1.png');
       fetch('/digits/2.png');
diff --git a/test/permissions.spec.js b/test/permissions.spec.ts
similarity index 99%
rename from test/permissions.spec.js
rename to test/permissions.spec.ts
index 31d1e5c432..455941d9d6 100644
--- a/test/permissions.spec.js
+++ b/test/permissions.spec.ts
@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT, LINUX, HEADLESS} = testOptions;
 
@@ -36,7 +36,7 @@ it.skip(WEBKIT)('should deny permission when not listed', async({page, server, c
 
 it.skip(WEBKIT)('should fail when bad permission is given', async({page, server, context}) => {
   await page.goto(server.EMPTY_PAGE);
-  let error = {};
+  let error: Error;
   await context.grantPermissions(['foo'], { origin: server.EMPTY_PAGE }).catch(e => error = e);
   expect(error.message).toContain('Unknown permission: foo');
 });
diff --git a/test/popup.spec.js b/test/popup.spec.ts
similarity index 93%
rename from test/popup.spec.js
rename to test/popup.spec.ts
index bd1f624fc7..6b7d49e39f 100644
--- a/test/popup.spec.js
+++ b/test/popup.spec.ts
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
 const {FFOX, CHROMIUM, WEBKIT, MAC} = testOptions;
 
@@ -31,7 +31,7 @@ it('should inherit user agent from browser context', async function({browser, se
     page.click('a'),
   ]);
   await popup.waitForLoadState('domcontentloaded');
-  const userAgent = await popup.evaluate(() => window.initialUserAgent);
+  const userAgent = await popup.evaluate(() => window["initialUserAgent"]);
   const request = await requestPromise;
   await context.close();
   expect(userAgent).toBe('hey');
@@ -63,7 +63,7 @@ it('should inherit extra headers from browser context', async function({browser,
   const page = await context.newPage();
   await page.goto(server.EMPTY_PAGE);
   const requestPromise = server.waitForRequest('/dummy.html');
-  await page.evaluate(url => window._popup = window.open(url), server.PREFIX + '/dummy.html');
+  await page.evaluate(url => window["_popup"] = window.open(url), server.PREFIX + '/dummy.html');
   const request = await requestPromise;
   await context.close();
   expect(request.headers['foo']).toBe('bar');
@@ -91,7 +91,7 @@ it('should inherit http credentials from browser context', async function({brows
   await page.goto(server.EMPTY_PAGE);
   const [popup] = await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(url => window._popup = window.open(url), server.PREFIX + '/title.html'),
+    page.evaluate(url => window["_popup"] = window.open(url), server.PREFIX + '/title.html'),
   ]);
   await popup.waitForLoadState('domcontentloaded');
   expect(await popup.title()).toBe('Woof-Woof');
@@ -159,7 +159,7 @@ it('should respect routes from browser context', async function({browser, server
   });
   await Promise.all([
     page.waitForEvent('popup'),
-    page.evaluate(url => window.__popup = window.open(url), server.EMPTY_PAGE),
+    page.evaluate(url => window["__popup"] = window.open(url), server.EMPTY_PAGE),
   ]);
   expect(intercepted).toBe(true);
   await context.close();
@@ -167,12 +167,12 @@ it('should respect routes from browser context', async function({browser, server
 
 it('BrowserContext.addInitScript should apply to an in-process popup', async function({browser, server}) {
   const context = await browser.newContext();
-  await context.addInitScript(() => window.injected = 123);
+  await context.addInitScript(() => window['injected'] = 123);
   const page = await context.newPage();
   await page.goto(server.EMPTY_PAGE);
   const injected = await page.evaluate(() => {
     const win = window.open('about:blank');
-    return win.injected;
+    return win['injected'];
   });
   await context.close();
   expect(injected).toBe(123);
@@ -180,7 +180,7 @@ it('BrowserContext.addInitScript should apply to an in-process popup', async fun
 
 it('BrowserContext.addInitScript should apply to a cross-process popup', async function({browser, server}) {
   const context = await browser.newContext();
-  await context.addInitScript(() => window.injected = 123);
+  await context.addInitScript(() => window['injected'] = 123);
   const page = await context.newPage();
   await page.goto(server.EMPTY_PAGE);
   const [popup] = await Promise.all([
@@ -205,7 +205,7 @@ it('should expose function from browser context', async function({browser, serve
   await page.goto(server.EMPTY_PAGE);
   const added = await page.evaluate(async () => {
     const win = window.open('about:blank');
-    return win.add(9, 4);
+    return win['add'](9, 4);
   });
   await context.close();
   expect(added).toBe(13);
@@ -230,7 +230,7 @@ it('should not dispatch binding on a closed page', async function({browser, serv
     }),
     page.evaluate(async () => {
       const win = window.open('about:blank');
-      win.add(9, 4);
+      win['add'](9, 4);
       win.close();
     }),
   ]);
diff --git a/test/proxy.spec.js b/test/proxy.spec.ts
similarity index 98%
rename from test/proxy.spec.js
rename to test/proxy.spec.ts
index 211cd02aa4..a4c9d0b739 100644
--- a/test/proxy.spec.js
+++ b/test/proxy.spec.ts
@@ -13,10 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const socks = require('socksv5');
-const utils = require('./utils');
+import socks from 'socksv5';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, MAC, HEADLESS} = testOptions;
 
 it('should use proxy', async ({browserType, defaultBrowserOptions, server}) => {
diff --git a/test/queryselector.spec.js b/test/queryselector.spec.ts
similarity index 97%
rename from test/queryselector.spec.js
rename to test/queryselector.spec.ts
index 1cc2f5bdde..5382813cde 100644
--- a/test/queryselector.spec.js
+++ b/test/queryselector.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should query existing element with css selector', async({page, server}) => {
diff --git a/test/request-continue.spec.js b/test/request-continue.spec.ts
similarity index 96%
rename from test/request-continue.spec.js
rename to test/request-continue.spec.ts
index f7b1335758..e032b461f7 100644
--- a/test/request-continue.spec.js
+++ b/test/request-continue.spec.ts
@@ -14,12 +14,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const { helper } = require('../lib/helper');
-const vm = require('vm');
+import fs from 'fs';
+import path from 'path';
+import { helper } from '../lib/helper';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, HEADLESS} = testOptions;
 
 it('should work', async({page, server}) => {
diff --git a/test/request-fulfill.spec.js b/test/request-fulfill.spec.ts
similarity index 96%
rename from test/request-fulfill.spec.js
rename to test/request-fulfill.spec.ts
index 80c5feda17..4dca89c22b 100644
--- a/test/request-fulfill.spec.js
+++ b/test/request-fulfill.spec.ts
@@ -14,12 +14,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const fs = require('fs');
-const path = require('path');
-const { helper } = require('../lib/helper');
-const vm = require('vm');
+import fs from 'fs';
+import path from 'path';
+import { helper } from '../lib/helper';
+import vm from 'vm';
 const {FFOX, CHROMIUM, WEBKIT, HEADLESS} = testOptions;
 
 it('should work', async({page, server}) => {
@@ -106,7 +106,7 @@ it('should stringify intercepted request response headers', async({page, server}
     route.fulfill({
       status: 200,
       headers: {
-        'foo': true
+        'foo': 'true'
       },
       body: 'Yo, page!'
     });
@@ -123,7 +123,7 @@ it('should not modify the headers sent to the server', async({page, server}) =>
   const interceptedRequests = [];
 
   //this is just to enable request interception, which disables caching in chromium
-  await page.route(server.PREFIX + '/unused');
+  await page.route(server.PREFIX + '/unused', () => {});
 
   server.setRoute('/something', (request, response) => {
     interceptedRequests.push(request);
diff --git a/test/screencast.spec.js b/test/screencast.spec.ts
similarity index 95%
rename from test/screencast.spec.js
rename to test/screencast.spec.ts
index 25f7baf6e0..5fe4b526d9 100644
--- a/test/screencast.spec.js
+++ b/test/screencast.spec.ts
@@ -13,7 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
+import { FirefoxBrowser } from '..';
 
 const fs = require('fs');
 const os = require('os');
@@ -22,6 +23,12 @@ const url = require('url');
 const {mkdtempAsync, removeFolderAsync} = require('./utils');
 
 const {FFOX, CHROMIUM, WEBKIT, MAC, LINUX, WIN, HEADLESS, USES_HOOKS} = testOptions;
+declare global {
+  interface FixtureState {
+    persistentDirectory: string;
+    firefox: FirefoxBrowser;
+  }  
+}
 
 registerFixture('persistentDirectory', async ({}, test) => {
   const persistentDirectory = await mkdtempAsync(path.join(os.tmpdir(), 'playwright-test-'));
diff --git a/test/selectors-css.spec.js b/test/selectors-css.spec.ts
similarity index 95%
rename from test/selectors-css.spec.js
rename to test/selectors-css.spec.ts
index 77caefa15b..23c393c8c9 100644
--- a/test/selectors-css.spec.js
+++ b/test/selectors-css.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should work for open shadow roots', async({page, server}) => {
@@ -102,7 +102,7 @@ it('should work with comma inside text', async({page}) => {
 
 it('should work with attribute selectors', async({page}) => {
   await page.setContent(`<div attr="hello world" attr2="hello-''>>foo=bar[]" attr3="] span"><span></span></div>`);
-  await page.evaluate(() => window.div = document.querySelector('div'));
+  await page.evaluate(() => window['div'] = document.querySelector('div'));
   const selectors = [
     `[attr="hello world"]`,
     `[attr = "hello world"]`,
@@ -118,8 +118,8 @@ it('should work with attribute selectors', async({page}) => {
     `[attr2 $="foo=bar[]"]`,
   ];
   for (const selector of selectors)
-    expect(await page.$eval(selector, e => e === div)).toBe(true);
-  expect(await page.$eval(`[attr*=hello] span`, e => e.parentNode === div)).toBe(true);
-  expect(await page.$eval(`[attr*=hello] >> span`, e => e.parentNode === div)).toBe(true);
-  expect(await page.$eval(`[attr3="] span"] >> span`, e => e.parentNode === div)).toBe(true);
+    expect(await page.$eval(selector, e => e === window['div'])).toBe(true);
+  expect(await page.$eval(`[attr*=hello] span`, e => e.parentNode === window['div'])).toBe(true);
+  expect(await page.$eval(`[attr*=hello] >> span`, e => e.parentNode === window['div'])).toBe(true);
+  expect(await page.$eval(`[attr3="] span"] >> span`, e => e.parentNode === window['div'])).toBe(true);
 });
diff --git a/test/selectors-misc.spec.js b/test/selectors-misc.spec.ts
similarity index 93%
rename from test/selectors-misc.spec.js
rename to test/selectors-misc.spec.ts
index 6277020d9a..862d3ca9a1 100644
--- a/test/selectors-misc.spec.js
+++ b/test/selectors-misc.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should work for open shadow roots', async({page, server}) => {
diff --git a/test/selectors-register.spec.js b/test/selectors-register.spec.ts
similarity index 88%
rename from test/selectors-register.spec.js
rename to test/selectors-register.spec.ts
index faa7d1402d..10db2e2758 100644
--- a/test/selectors-register.spec.js
+++ b/test/selectors-register.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('should work', async ({playwright, page}) => {
@@ -34,7 +34,7 @@ it('should work', async ({playwright, page}) => {
   });
   await utils.registerEngine(playwright, 'tag', `(${createTagSelector.toString()})()`);
   await page.setContent('<div><span></span></div><div></div>');
-  expect(await playwright.selectors._createSelector('tag', await page.$('div'))).toBe('DIV');
+  expect(await (playwright.selectors as any)._createSelector('tag', await page.$('div'))).toBe('DIV');
   expect(await page.$eval('tag=DIV', e => e.nodeName)).toBe('DIV');
   expect(await page.$eval('tag=SPAN', e => e.nodeName)).toBe('SPAN');
   expect(await page.$$eval('tag=DIV', es => es.length)).toBe(2);
@@ -54,26 +54,26 @@ it('should work in main and isolated world', async ({playwright, page}) => {
   const createDummySelector = () => ({
     create(root, target) { },
     query(root, selector) {
-      return window.__answer;
+      return window['__answer'];
     },
     queryAll(root, selector) {
-      return [document.body, document.documentElement, window.__answer];
+      return [document.body, document.documentElement, window['__answer']];
     }
   });
   await utils.registerEngine(playwright, 'main', createDummySelector);
   await utils.registerEngine(playwright, 'isolated', createDummySelector, { contentScript: true });
   await page.setContent('<div><span><section></section></span></div>');
-  await page.evaluate(() => window.__answer = document.querySelector('span'));
+  await page.evaluate(() => window['__answer'] = document.querySelector('span'));
   // Works in main if asked.
   expect(await page.$eval('main=ignored', e => e.nodeName)).toBe('SPAN');
   expect(await page.$eval('css=div >> main=ignored', e => e.nodeName)).toBe('SPAN');
-  expect(await page.$$eval('main=ignored', es => window.__answer !== undefined)).toBe(true);
+  expect(await page.$$eval('main=ignored', es => window['__answer'] !== undefined)).toBe(true);
   expect(await page.$$eval('main=ignored', es => es.filter(e => e).length)).toBe(3);
   // Works in isolated by default.
   expect(await page.$('isolated=ignored')).toBe(null);
   expect(await page.$('css=div >> isolated=ignored')).toBe(null);
   // $$eval always works in main, to avoid adopting nodes one by one.
-  expect(await page.$$eval('isolated=ignored', es => window.__answer !== undefined)).toBe(true);
+  expect(await page.$$eval('isolated=ignored', es => window['__answer'] !== undefined)).toBe(true);
   expect(await page.$$eval('isolated=ignored', es => es.filter(e => e).length)).toBe(3);
   // At least one engine in main forces all to be in main.
   expect(await page.$eval('main=ignored >> isolated=ignored', e => e.nodeName)).toBe('SPAN');
diff --git a/test/selectors-text.spec.js b/test/selectors-text.spec.ts
similarity index 93%
rename from test/selectors-text.spec.js
rename to test/selectors-text.spec.ts
index 6ebc2af43d..04cc976076 100644
--- a/test/selectors-text.spec.js
+++ b/test/selectors-text.spec.ts
@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const path = require('path');
-const utils = require('./utils');
+import path from 'path';
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL, USES_HOOKS} = testOptions;
 
 it('query', async ({page}) => {
@@ -101,18 +101,18 @@ it('query', async ({page}) => {
 
 it('create', async ({playwright, page}) => {
   await page.setContent(`<div>yo</div><div>"ya</div><div>ye ye</div>`);
-  expect(await playwright.selectors._createSelector('text', await page.$('div'))).toBe('yo');
-  expect(await playwright.selectors._createSelector('text', await page.$('div:nth-child(2)'))).toBe('"\\"ya"');
-  expect(await playwright.selectors._createSelector('text', await page.$('div:nth-child(3)'))).toBe('"ye ye"');
+  expect(await (playwright.selectors as any)._createSelector('text', await page.$('div'))).toBe('yo');
+  expect(await (playwright.selectors as any)._createSelector('text', await page.$('div:nth-child(2)'))).toBe('"\\"ya"');
+  expect(await (playwright.selectors as any)._createSelector('text', await page.$('div:nth-child(3)'))).toBe('"ye ye"');
 
   await page.setContent(`<div>yo</div><div>yo<div>ya</div>hey</div>`);
-  expect(await playwright.selectors._createSelector('text', await page.$('div:nth-child(2)'))).toBe('hey');
+  expect(await (playwright.selectors as any)._createSelector('text', await page.$('div:nth-child(2)'))).toBe('hey');
 
   await page.setContent(`<div> yo <div></div>ya</div>`);
-  expect(await playwright.selectors._createSelector('text', await page.$('div'))).toBe('yo');
+  expect(await (playwright.selectors as any)._createSelector('text', await page.$('div'))).toBe('yo');
 
   await page.setContent(`<div> "yo <div></div>ya</div>`);
-  expect(await playwright.selectors._createSelector('text', await page.$('div'))).toBe('" \\"yo "');
+  expect(await (playwright.selectors as any)._createSelector('text', await page.$('div'))).toBe('" \\"yo "');
 });
 
 it('should be case sensitive if quotes are specified', async({page}) => {
diff --git a/test/wait-for-function.spec.js b/test/wait-for-function.spec.ts
similarity index 82%
rename from test/wait-for-function.spec.js
rename to test/wait-for-function.spec.ts
index b1060d52a0..2557f11ddb 100644
--- a/test/wait-for-function.spec.js
+++ b/test/wait-for-function.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL} = testOptions;
 
 it('should timeout', async({page, server}) => {
@@ -28,14 +28,14 @@ it('should timeout', async({page, server}) => {
 
 it('should accept a string', async({page, server}) => {
   const watchdog = page.waitForFunction('window.__FOO === 1');
-  await page.evaluate(() => window.__FOO = 1);
+  await page.evaluate(() => window['__FOO'] = 1);
   await watchdog;
 });
 
 it('should work when resolved right before execution context disposal', async({page, server}) => {
-  await page.addInitScript(() => window.__RELOADED = true);
+  await page.addInitScript(() => window['__RELOADED'] = true);
   await page.waitForFunction(() => {
-    if (!window.__RELOADED)
+    if (!window['__RELOADED'])
       window.location.reload();
     return true;
   });
@@ -44,11 +44,11 @@ it('should work when resolved right before execution context disposal', async({p
 it('should poll on interval', async({page, server}) => {
   const polling = 100;
   const timeDelta = await page.waitForFunction(() => {
-    if (!window.__startTime) {
-      window.__startTime = Date.now();
+    if (!window['__startTime']) {
+      window['__startTime'] = Date.now();
       return false;
     }
-    return Date.now() - window.__startTime;
+    return Date.now() - window['__startTime'];
   }, {}, {polling});
   expect(await timeDelta.jsonValue()).not.toBeLessThan(polling);
 });
@@ -58,8 +58,8 @@ it('should avoid side effects after timeout', async({page, server}) => {
   page.on('console', () => ++counter);
 
   const error = await page.waitForFunction(() => {
-    window.counter = (window.counter || 0) + 1;
-    console.log(window.counter);
+    window['counter'] = (window['counter'] || 0) + 1;
+    console.log(window['counter']);
   }, {}, { polling: 1, timeout: 1000 }).catch(e => e);
 
   const savedCounter = counter;
@@ -70,13 +70,13 @@ it('should avoid side effects after timeout', async({page, server}) => {
 });
 
 it('should throw on polling:mutation', async({page, server}) => {
-  const error = await page.waitForFunction(() => true, {}, {polling: 'mutation'}).catch(e => e);
+  const error = await page.waitForFunction(() => true, {}, {polling: 'mutation' as any}).catch(e => e);
   expect(error.message).toContain('Unknown polling option: mutation');
 });
 
 it('should poll on raf', async({page, server}) => {
-  const watchdog = page.waitForFunction(() => window.__FOO === 'hit', {}, {polling: 'raf'});
-  await page.evaluate(() => window.__FOO = 'hit');
+  const watchdog = page.waitForFunction(() => window['__FOO'] === 'hit', {}, {polling: 'raf'});
+  await page.evaluate(() => window['__FOO'] = 'hit');
   await watchdog;
 });
 
@@ -87,15 +87,16 @@ it('should fail with predicate throwing on first call', async({page, server}) =>
 
 it('should fail with predicate throwing sometimes', async({page, server}) => {
   const error = await page.waitForFunction(() => {
-    window.counter = (window.counter || 0) + 1;
-    if (window.counter === 3)
+    window['counter'] = (window['counter'] || 0) + 1;
+    if (window['counter'] === 3)
       throw new Error('Bad counter!');
-    return window.counter === 5 ? 'result' : false;
+    return window['counter'] === 5 ? 'result' : false;
   }).catch(e => e);
   expect(error.message).toContain('Bad counter!');
 });
 
 it('should fail with ReferenceError on wrong page', async({page, server}) => {
+  // @ts-ignore
   const error = await page.waitForFunction(() => globalVar === 123).catch(e => e);
   expect(error.message).toContain('globalVar');
 });
@@ -105,8 +106,8 @@ it('should work with strict CSP policy', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   let error = null;
   await Promise.all([
-    page.waitForFunction(() => window.__FOO === 'hit', {}, {polling: 'raf'}).catch(e => error = e),
-    page.evaluate(() => window.__FOO = 'hit')
+    page.waitForFunction(() => window['__FOO'] === 'hit', {}, {polling: 'raf'}).catch(e => error = e),
+    page.evaluate(() => window['__FOO'] = 'hit')
   ]);
   expect(error).toBe(null);
 });
@@ -114,7 +115,7 @@ it('should work with strict CSP policy', async({page, server}) => {
 it('should throw on bad polling value', async({page, server}) => {
   let error = null;
   try {
-    await page.waitForFunction(() => !!document.body, {}, {polling: 'unknown'});
+    await page.waitForFunction(() => !!document.body, {}, {polling: 'unknown' as any});
   } catch (e) {
     error = e;
   }
@@ -169,11 +170,11 @@ it('should respect default timeout', async({page, playwright}) => {
 
 it('should disable timeout when its set to 0', async({page}) => {
   const watchdog = page.waitForFunction(() => {
-    window.__counter = (window.__counter || 0) + 1;
-    return window.__injected;
+    window['__counter'] = (window['__counter'] || 0) + 1;
+    return window["__injected"];
   }, {}, {timeout: 0, polling: 10});
-  await page.waitForFunction(() => window.__counter > 10);
-  await page.evaluate(() => window.__injected = true);
+  await page.waitForFunction(() => window['__counter'] > 10);
+  await page.evaluate(() => window["__injected"] = true);
   await watchdog;
 });
 
@@ -186,16 +187,16 @@ it('should survive cross-process navigation', async({page, server}) => {
   expect(fooFound).toBe(false);
   await page.goto(server.CROSS_PROCESS_PREFIX + '/grid.html');
   expect(fooFound).toBe(false);
-  await page.evaluate(() => window.__FOO = 1);
+  await page.evaluate(() => window['__FOO'] = 1);
   await waitForFunction;
   expect(fooFound).toBe(true);
 });
 
 it('should survive navigations', async({page, server}) => {
-  const watchdog = page.waitForFunction(() => window.__done);
+  const watchdog = page.waitForFunction(() => window['__done']);
   await page.goto(server.EMPTY_PAGE);
   await page.goto(server.PREFIX + '/consolelog.html');
-  await page.evaluate(() => window.__done = true);
+  await page.evaluate(() => window['__done'] = true);
   await watchdog;
 });
 
diff --git a/test/wait-for-selector.spec.js b/test/wait-for-selector.spec.ts
similarity index 97%
rename from test/wait-for-selector.spec.js
rename to test/wait-for-selector.spec.ts
index 9ea8f417f1..0c55822706 100644
--- a/test/wait-for-selector.spec.js
+++ b/test/wait-for-selector.spec.ts
@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
 
-const utils = require('./utils');
+import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, CHANNEL} = testOptions;
 
 async function giveItTimeToLog(frame) {
@@ -28,13 +28,15 @@ const addElement = tag => document.body.appendChild(document.createElement(tag))
 it('should throw on waitFor', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
   let error;
-  await page.waitForSelector('*', { waitFor: 'attached' }).catch(e => error = e);
+  await page.waitForSelector('*', { waitFor: 'attached' } as any).catch(e => error = e);
   expect(error.message).toContain('options.waitFor is not supported, did you mean options.state?');
 });
 
 it('should tolerate waitFor=visible', async({page, server}) => {
   await page.goto(server.EMPTY_PAGE);
-  await page.waitForSelector('*', { waitFor: 'visible' }).catch(e => error = e);
+  let error = false;
+  await page.waitForSelector('*', { waitFor: 'visible' } as any).catch(() => error = true);
+  expect(error).toBe(false);
 });
 
 it('should immediately resolve promise if node exists', async({page, server}) => {
@@ -316,25 +318,25 @@ it('should have correct stack trace for timeout', async({page, server}) => {
 
 it('should throw for unknown state option', async({page, server}) => {
   await page.setContent('<section>test</section>');
-  const error = await page.waitForSelector('section', { state: 'foo' }).catch(e => e);
+  const error = await page.waitForSelector('section', { state: 'foo' as any}).catch(e => e);
   expect(error.message).toContain('state: expected one of (attached|detached|visible|hidden)');
 });
 
 it('should throw for visibility option', async({page, server}) => {
   await page.setContent('<section>test</section>');
-  const error = await page.waitForSelector('section', { visibility: 'hidden' }).catch(e => e);
+  const error = await page.waitForSelector('section', { visibility: 'hidden' } as any).catch(e => e);
   expect(error.message).toContain('options.visibility is not supported, did you mean options.state?');
 });
 
 it('should throw for true state option', async({page, server}) => {
   await page.setContent('<section>test</section>');
-  const error = await page.waitForSelector('section', { state: true }).catch(e => e);
+  const error = await page.waitForSelector('section', { state: true as any }).catch(e => e);
   expect(error.message).toContain('state: expected one of (attached|detached|visible|hidden)');
 });
 
 it('should throw for false state option', async({page, server}) => {
   await page.setContent('<section>test</section>');
-  const error = await page.waitForSelector('section', { state: false }).catch(e => e);
+  const error = await page.waitForSelector('section', { state: false as any }).catch(e => e);
   expect(error.message).toContain('state: expected one of (attached|detached|visible|hidden)');
 });
 
diff --git a/test/workers.spec.js b/test/workers.spec.ts
similarity index 96%
rename from test/workers.spec.js
rename to test/workers.spec.ts
index e6c9da953b..ce195c06e8 100644
--- a/test/workers.spec.js
+++ b/test/workers.spec.ts
@@ -14,7 +14,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('./base.fixture');
+import './base.fixture';
+import { ConsoleMessage } from '..';
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
@@ -52,7 +53,7 @@ it('should report console logs', async function({page}) {
 });
 
 it('should have JSHandles for console logs', async function({page}) {
-  const logPromise = new Promise(x => page.on('console', x));
+  const logPromise = new Promise<ConsoleMessage>(x => page.on('console', x));
   await page.evaluate(() => new Worker(URL.createObjectURL(new Blob(['console.log(1,2,3,this)'], {type: 'application/javascript'}))));
   const log = await logPromise;
   expect(log.text()).toBe('1 2 3 JSHandle@object');
@@ -68,7 +69,7 @@ it('should evaluate', async function({page}) {
 });
 
 it('should report errors', async function({page}) {
-  const errorPromise = new Promise(x => page.on('pageerror', x));
+  const errorPromise = new Promise<Error>(x => page.on('pageerror', x));
   await page.evaluate(() => new Worker(URL.createObjectURL(new Blob([`
     setTimeout(() => {
       // Do a console.log just to check that we do not confuse it with an error.
diff --git a/utils/testserver/index.d.ts b/utils/testserver/index.d.ts
index 3d1b8614a6..ac5f537514 100644
--- a/utils/testserver/index.d.ts
+++ b/utils/testserver/index.d.ts
@@ -21,9 +21,9 @@ export class TestServer {
   enableGzip(path: string);
   setCSP(path: string, csp: string);
   stop(): Promise<void>;
-  setRoute(path: string, handler: (message: IncomingMessage, response: ServerResponse) => void);
+  setRoute(path: string, handler: (message: IncomingMessage & {postBody: Buffer}, response: ServerResponse) => void);
   setRedirect(from: string, to: string);
-  waitForRequest(path: string): Promise<IncomingMessage>;
+  waitForRequest(path: string): Promise<IncomingMessage & {postBody: Buffer}>;
   reset();
   serveFile(request: IncomingMessage, response: ServerResponse, pathName: string);