feat(@angular/build): add reporter output file option for unit-test

The experimental `unit-test` builder now contains an additional option
named `outputFile` that supports configuring the output file for the reporter.
This option is currently only used by the `vitest` runner.
See https://vitest.dev/config/#outputfile

Usage example:

```
ng test --no-watch --reporter=json --output-file=results/unit-test.json
```

Author: cexbrayat

goldens/public-api/angular/build/index.api.md

@@ -223,6 +223,7 @@ export type UnitTestBuilderOptions = {
     debug?: boolean;
     exclude?: string[];
     include?: string[];
+    outputFile?: string;
     progress?: boolean;
     providersFile?: string;
     reporters?: SchemaReporter[];

packages/angular/build/src/builders/unit-test/options.ts

@@ -65,6 +65,7 @@ export async function normalizeOptions(
     tsConfig,
     buildProgress: progress,
     reporters: normalizeReporterOption(options.reporters),
+    outputFile: options.outputFile,
     browsers,
     watch: options.watch ?? isTTY(),
     debug: options.debug ?? false,

packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts

@@ -127,8 +127,8 @@ export class VitestExecutor implements TestExecutor {
   }
 
   private async initializeVitest(): Promise<Vitest> {
-    const { codeCoverage, reporters, workspaceRoot, browsers, debug, watch } = this.options;
-
+    const { codeCoverage, reporters, outputFile, workspaceRoot, browsers, debug, watch } =
+      this.options;
     let vitestNodeModule;
     try {
       vitestNodeModule = await loadEsmModule<typeof import('vitest/node')>('vitest/node');
@@ -188,6 +188,7 @@ export class VitestExecutor implements TestExecutor {
         name: 'base',
         include: [],
         reporters: reporters ?? ['default'],
+        outputFile,
         watch,
         coverage: generateCoverageOption(codeCoverage),
         ...debugOptions,

packages/angular/build/src/builders/unit-test/schema.json

@@ -124,6 +124,10 @@
         ]
       }
     },
+    "outputFile": {
+      "type": "string",
+      "description": "The file to output the test report to. If not specified, the test runner will output to the console."
+    },
     "providersFile": {
       "type": "string",
       "description": "TypeScript file that exports an array of Angular providers to use during test execution. The array must be a default export.",

packages/angular/build/src/builders/unit-test/tests/options/reporter_and_output_file_spec.ts

@@ -0,0 +1,46 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import { execute } from '../../index';
+import {
+  BASE_OPTIONS,
+  describeBuilder,
+  UNIT_TEST_BUILDER_INFO,
+  setupApplicationTarget,
+} from '../setup';
+
+describeBuilder(execute, UNIT_TEST_BUILDER_INFO, (harness) => {
+  describe('Options: "reporter" and "outputFile"', () => {
+    beforeEach(async () => {
+      setupApplicationTarget(harness);
+    });
+
+    it(`should output a JSON report`, async () => {
+      await harness.removeFile('src/app/app.component.spec.ts');
+      await harness.writeFiles({
+        'src/app/services/test.service.spec.ts': `
+          describe('TestService', () => {
+            it('should succeed', () => {
+              expect(true).toBe(true);
+            });
+          });`,
+      });
+
+      harness.useTarget('test', {
+        ...BASE_OPTIONS,
+        reporters: ['json'],
+        outputFile: 'test-report.json',
+      });
+
+      const { result } = await harness.executeOnce();
+      expect(result?.success).toBeTrue();
+      const reportContent = await harness.readFile('test-report.json');
+      expect(reportContent).toContain('TestService');
+    });
+  });
+});