fix(runner): friendly error message instead of "digests do not match" (#15939)

packages/playwright-test/src/fixtures.ts

@@ -300,8 +300,14 @@ export class FixtureRunner {
   setPool(pool: FixturePool) {
     if (!this.testScopeClean)
       throw new Error('Did not teardown test scope');
-    if (this.pool && pool.digest !== this.pool.digest)
+    if (this.pool && pool.digest !== this.pool.digest) {
-      throw new Error('Digests do not match');
+      throw new Error([
+        `Playwright detected inconsistent test.use() options.`,
+        `Most common mistakes that lead to this issue:`,
+        `  - Calling test.use() outside of the test file, for example in a common helper.`,
+        `  - One test file imports from another test file.`,
+      ].join('\n'));
+    }
     this.pool = pool;
   }
 

tests/playwright-test/fixture-errors.spec.ts

@@ -584,3 +584,39 @@ test('should not run user fn when require fixture has failed', async ({ runInlin
     '%%foo',
   ]);
 });
+
+test('should provide helpful error message when digests do not match', async ({ runInlineTest }) => {
+  const result = await runInlineTest({
+    'helper.ts': `
+      export const test = pwt.test.extend({
+        foo: [ async ({}, use) => use(), { scope: 'worker' } ],
+      });
+
+      test.use({ foo: 'foo' });
+    `,
+    'a.spec.ts': `
+      import { test } from './helper';
+
+      test('test-a', ({ foo }) => {
+        expect(foo).toBe('foo');
+      });
+    `,
+    'b.spec.ts': `
+      import { test } from './helper';
+
+      test('test-b', ({ foo }) => {
+        expect(foo).toBe('foo');
+      });
+    `,
+    'c.spec.ts': `
+      import { test } from './helper';
+
+      test('test-c', ({ foo }) => {
+        expect(foo).toBe('foo');
+      });
+    `,
+  }, { workers: 1 });
+  expect(result.exitCode).toBe(1);
+  expect(result.failed).toBe(1);
+  expect(stripAnsi(result.output)).toContain('Playwright detected inconsistent test.use() options.');
+});