docs(test-runners-java.md): added testng implementation (#26537)

Resolves microsoft/playwright-java#1343

docs/src/test-runners-java.md

@@ -278,3 +278,77 @@ Also, Playwright command line tools can be run with :
 ```bash
 ./gradlew playwright --args="help"
 ```
+
+## TestNG
+
+In [TestNG](https://testng.org/) you can initialize [Playwright] and [Browser] in [@BeforeClass](https://javadoc.io/doc/org.testng/testng/latest/org/testng/annotations/BeforeClass.html) method and
+destroy them in [@AfterClass](https://javadoc.io/doc/org.testng/testng/latest/org/testng/annotations/AfterClass.html). In the example below all three test methods use the same
+[Browser]. Each test uses its own [BrowserContext] and [Page].
+
+```java
+package org.example;
+
+import com.microsoft.playwright.Browser;
+import com.microsoft.playwright.BrowserContext;
+import com.microsoft.playwright.Page;
+import com.microsoft.playwright.Playwright;
+import org.testng.annotations.*;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertTrue;
+
+public class TestExample {
+  // Shared between all tests in this class.
+  Playwright playwright;
+  Browser browser;
+
+  // New instance for each test method.
+  BrowserContext context;
+  Page page;
+
+  @BeforeClass
+  void launchBrowser() {
+    playwright = Playwright.create();
+    browser = playwright.chromium().launch();
+  }
+
+  @AfterClass
+  void closeBrowser() {
+    playwright.close();
+  }
+
+  @BeforeMethod
+  void createContextAndPage() {
+    context = browser.newContext();
+    page = context.newPage();
+  }
+
+  @AfterMethod
+  void closeContext() {
+    context.close();
+  }
+
+  @Test
+  void shouldClickButton() {
+    page.navigate("data:text/html,<script>var result;</script><button onclick='result=\"Clicked\"'>Go</button>");
+    page.locator("button").click();
+    assertEquals("Clicked", page.evaluate("result"));
+  }
+
+  @Test
+  void shouldCheckTheBox() {
+    page.setContent("<input id='checkbox' type='checkbox'></input>");
+    page.locator("input").check();
+    assertTrue((Boolean) page.evaluate("() => window['checkbox'].checked"));
+  }
+
+  @Test
+  void shouldSearchWiki() {
+    page.navigate("https://www.wikipedia.org/");
+    page.locator("input[name=\"search\"]").click();
+    page.locator("input[name=\"search\"]").fill("playwright");
+    page.locator("input[name=\"search\"]").press("Enter");
+    assertEquals("https://en.wikipedia.org/wiki/Playwright", page.url());
+  }
+}
+```