fix(@angular/build): defer empty test discovery to Vitest

Remove the unit-test builder pre-check that failed before Vitest ran so
passWithNoTests in runner config can succeed in CI when no specs exist yet.

Author: ant1quar

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

@@ -195,14 +195,6 @@ export async function getVitestBuildOptions(
 
   // Find test files
   const testFiles = await findTests(include, exclude, workspaceRoot, projectSourceRoot);
-  if (testFiles.length === 0) {
-    throw new Error(
-      'No tests found matching the following patterns:\n' +
-        `- Included: ${include.join(', ')}\n` +
-        (exclude.length ? `- Excluded: ${exclude.join(', ')}\n` : '') +
-        `\nPlease check the 'test' target configuration in your project's 'angular.json' file.`,
-    );
-  }
 
   const entryPoints = getTestEntrypoints(testFiles, {
     projectSourceRoot,

packages/angular/build/src/builders/unit-test/tests/behavior/pass-with-no-tests_spec.ts

@@ -0,0 +1,58 @@
+/**
+ * @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('Behavior: no test files', () => {
+    beforeEach(() => {
+      setupApplicationTarget(harness);
+    });
+
+    it('should fail when no tests are discovered and passWithNoTests is not enabled', async () => {
+      harness.useTarget('test', {
+        ...BASE_OPTIONS,
+        include: ['**/__no_matching_tests__.spec.ts'],
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBeFalse();
+    });
+
+    it('should succeed when no tests are discovered and passWithNoTests is enabled in runnerConfig', async () => {
+      harness.useTarget('test', {
+        ...BASE_OPTIONS,
+        include: ['**/__no_matching_tests__.spec.ts'],
+        runnerConfig: 'vitest.config.mts',
+      });
+
+      harness.writeFile(
+        'vitest.config.mts',
+        `
+        import { defineConfig } from 'vitest/config';
+        export default defineConfig({
+          test: {
+            passWithNoTests: true,
+          },
+        });
+      `,
+      );
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBeTrue();
+    });
+  });
+});