refactor(@angular/build): provide karma runner for unit-test builder

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

@@ -22,6 +22,7 @@ import { ResultKind } from '../application/results';
 import { OutputHashing } from '../application/schema';
 import { writeTestFiles } from '../karma/application_builder';
 import { findTests, getTestEntrypoints } from '../karma/find-tests';
+import { useKarmaBuilder } from './karma-bridge';
 import { normalizeOptions } from './options';
 import type { Schema as UnitTestOptions } from './schema';
 
@@ -52,6 +53,14 @@ export async function* execute(
   const normalizedOptions = await normalizeOptions(context, projectName, options);
   const { projectSourceRoot, workspaceRoot, runnerName } = normalizedOptions;
 
+  // Translate options and use karma builder directly if specified
+  if (runnerName === 'karma') {
+    const karmaBridge = await useKarmaBuilder(context, normalizedOptions);
+    yield* karmaBridge;
+
+    return;
+  }
+
   if (runnerName !== 'vitest') {
     context.logger.error('Unknown test runner: ' + runnerName);
 

packages/angular/build/src/builders/unit-test/karma-bridge.ts

@@ -0,0 +1,53 @@
+/**
+ * @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 type { BuilderContext, BuilderOutput } from '@angular-devkit/architect';
+import type { ApplicationBuilderInternalOptions } from '../application/options';
+import type { KarmaBuilderOptions } from '../karma';
+import type { NormalizedUnitTestOptions } from './options';
+
+export async function useKarmaBuilder(
+  context: BuilderContext,
+  unitTestOptions: NormalizedUnitTestOptions,
+): Promise<AsyncIterable<BuilderOutput>> {
+  const buildTargetOptions = (await context.validateOptions(
+    await context.getTargetOptions(unitTestOptions.buildTarget),
+    await context.getBuilderNameForTarget(unitTestOptions.buildTarget),
+  )) as unknown as ApplicationBuilderInternalOptions;
+
+  const options: KarmaBuilderOptions = {
+    tsConfig: unitTestOptions.tsConfig,
+    polyfills: buildTargetOptions.polyfills,
+    assets: buildTargetOptions.assets,
+    scripts: buildTargetOptions.scripts,
+    styles: buildTargetOptions.styles,
+    inlineStyleLanguage: buildTargetOptions.inlineStyleLanguage,
+    stylePreprocessorOptions: buildTargetOptions.stylePreprocessorOptions,
+    externalDependencies: buildTargetOptions.externalDependencies,
+    loader: buildTargetOptions.loader,
+    define: buildTargetOptions.define,
+    include: unitTestOptions.include,
+    exclude: unitTestOptions.exclude,
+    sourceMap: buildTargetOptions.sourceMap,
+    progress: buildTargetOptions.progress,
+    watch: unitTestOptions.watch,
+    poll: buildTargetOptions.poll,
+    preserveSymlinks: buildTargetOptions.preserveSymlinks,
+    browsers: unitTestOptions.browsers?.join(','),
+    codeCoverage: unitTestOptions.codeCoverage,
+    codeCoverageExclude: unitTestOptions.codeCoverageExclude,
+    fileReplacements: buildTargetOptions.fileReplacements,
+    reporters: unitTestOptions.reporters,
+    webWorkerTsConfig: buildTargetOptions.webWorkerTsConfig,
+    aot: buildTargetOptions.aot,
+  };
+
+  const { execute } = await import('../karma');
+
+  return execute(options, context);
+}

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

@@ -16,7 +16,7 @@
     "runner": {
       "type": "string",
       "description": "The name of the test runner to use for test execution.",
-      "enum": ["vitest"]
+      "enum": ["karma", "vitest"]
     },
     "browsers": {
       "description": "A list of browsers to use for test execution. If undefined, jsdom on Node.js will be used instead of a browser.",