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 +1,53 @@
+import assert from 'node:assert/strict';
+import { applyVitestBuilder } from '../../utils/vitest';
+import { ng, noSilentNg } from '../../utils/process';
+import { installPackage } from '../../utils/packages';
+import { expectFileToExist, readFile, writeFile } from '../../utils/fs';
+import { stripVTControlCharacters } from 'node:util';
+
+export default async function (): Promise<void> {
+  await applyVitestBuilder();
+  await installPackage('playwright@1');
+  await installPackage('@vitest/browser-playwright@4');
+  await installPackage('@vitest/coverage-v8@4');
+  await ng('generate', 'component', 'my-comp');
+
+  // Add a failing test to verify source map support
+  await writeFile(
+    'src/app/failing.spec.ts',
+    `
+      describe('Failing Test', () => {
+        it('should fail', () => {
+          expect(true).toBe(false);
+        });
+      });
+    `,
+  );
+
+  try {
+    await noSilentNg('test', '--no-watch', '--browsers', 'chromiumHeadless', '--coverage');
+    throw new Error('Expected "ng test" to fail.');
+  } catch (error: any) {
+    const stdout = stripVTControlCharacters(error.stdout || error.message);
+    console.log('STDOUT: ', stdout);
+    // We expect the failure from failing.spec.ts
+    assert.match(stdout, /1 failed/, 'Expected 1 test to fail.');
+    // Check that the stack trace points to the correct file
+    assert.match(
+      stdout,
+      /\\bsrc[\\/\\\\]app[\\/\\\\]failing\\.spec\\.ts:4:\\d+/,
+      'Expected stack trace to point to the source file.',
+    );
+  }
+
+  // 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\.component\.ts/,
+    'Expected coverage report to contain app.component.ts.',
+  );
+}