test(@angular/build): add E2E test for Vitest browser mode with coverage

This test ensures that stack traces map correctly to source files and that coverage reports are generated when running Vitest in browser mode with coverage enabled. This provides validation for the current implementation and will help verify future refactors removing the source-map-support dependency.

Author: clydin

tests/e2e/tests/vitest/browser-coverage-sourcemaps.ts

@@ -0,0 +1,31 @@
+import assert from 'node:assert/strict';
+import { applyVitestBuilder } from '../../utils/vitest';
+import { ng } from '../../utils/process';
+import { installPackage } from '../../utils/packages';
+import { expectFileToExist, readFile } from '../../utils/fs';
+
+export default async function (): Promise<void> {
+  await applyVitestBuilder();
+  await installPackage('playwright@1');
+  await installPackage('@vitest/browser-playwright@4');
+  await installPackage('@vitest/coverage-v8@4');
+
+  // Run tests with coverage in browser mode.
+  // We use the default passing tests generated for the project.
+  const { stdout } = await ng('test', '--no-watch', '--browsers', 'chromiumHeadless', '--coverage');
+
+  // Verify that tests passed
+  assert.match(stdout, /pass/, 'Expected tests to run successfully.');
+
+  // Verify that coverage files are generated
+  const coverageJsonPath = 'coverage/test-project/coverage-final.json';
+  await expectFileToExist(coverageJsonPath);
+
+  const coverageContent = await readFile(coverageJsonPath);
+  assert.match(coverageContent, /app\.ts/, 'Expected coverage report to contain app.ts.');
+  assert.doesNotMatch(
+    coverageContent,
+    /\.spec\.ts/,
+    'Expected coverage report to not contain .spec.ts files.',
+  );
+}