fix(@angular/build): allow TestBed provider configuration with vitest unit-testing

The experimental `unit-test` builder with the `vitest` runner configured
can now specify an Angular providers file via the `providersFile` option.
This allows the TestBed initialization to use the providers defined in
this file for all executed tests. The contents of the providers file should
include a default export with an array of one or more Angular providers.
As an example:
```
import { provideZonelessChangeDetection } from '@angular/core';

export default [
  provideZonelessChangeDetection(),
];

```

Author: clydin

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

@@ -142,15 +142,28 @@ export async function* execute(
     loadContent: async () => {
       const contents: string[] = [
         // Initialize the Angular testing environment
+        `import { NgModule } from '@angular/core';`,
         `import { getTestBed, ɵgetCleanupHook as getCleanupHook } from '@angular/core/testing';`,
         `import { BrowserTestingModule, platformBrowserTesting } from '@angular/platform-browser/testing';`,
         `import { beforeEach, afterEach } from 'vitest';`,
         '',
+        normalizedOptions.providersFile
+          ? `import providers from './${path
+              .relative(projectSourceRoot, normalizedOptions.providersFile)
+              .replace(/.[mc]?ts$/, '')
+              .replace(/\\/g, '/')}'`
+          : 'const providers = [];',
+        '',
         // Same as https://github.com/angular/angular/blob/05a03d3f975771bb59c7eefd37c01fa127ee2229/packages/core/testing/src/test_hooks.ts#L21-L29
         `beforeEach(getCleanupHook(false));`,
         `afterEach(getCleanupHook(true));`,
         '',
-        `getTestBed().initTestEnvironment(BrowserTestingModule, platformBrowserTesting(), {`,
+        `@NgModule({`,
+        `  providers,`,
+        `})`,
+        `export class TestModule {}`,
+        '',
+        `getTestBed().initTestEnvironment([BrowserTestingModule, TestModule], platformBrowserTesting(), {`,
         `  errorOnUnknownElements: true,`,
         `  errorOnUnknownProperties: true,`,
         '});',

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

@@ -52,6 +52,7 @@ export async function normalizeOptions(
     reporters,
     browsers,
     watch,
+    providersFile: options.providersFile && path.join(workspaceRoot, options.providersFile),
   };
 }
 

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

@@ -65,6 +65,11 @@
       "items": {
         "type": "string"
       }
+    },
+    "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.",
+      "minLength": 1
     }
   },
   "additionalProperties": false,