refactor: add initial Jest e2e test

This test generates an `ng new` project, updates it to use Jest for test executions, and then runs `ng test` and checks for the experimental notice.

Author: dgp1130

tests/legacy-cli/e2e/tests/jest/basic.ts

@@ -0,0 +1,12 @@
+import { applyJestBuilder } from '../../utils/jest';
+import { ng } from '../../utils/process';
+
+export default async function (): Promise<void> {
+  await applyJestBuilder();
+
+  const { stderr } = await ng('test');
+
+  if (!stderr.includes('Jest builder is currently EXPERIMENTAL')) {
+    throw new Error(`No experimental notice in stderr.\nSTDERR:\n\n${stderr}`);
+  }
+}

tests/legacy-cli/e2e/utils/jest.ts

@@ -0,0 +1,29 @@
+import { silentNpm } from './process';
+import { updateJsonFile } from './project';
+
+/** Updates the `test` builder in the current workspace to use Jest with the given options. */
+export async function applyJestBuilder(
+  options: {} = {
+    tsConfig: 'tsconfig.spec.json',
+    polyfills: ['zone.js', 'zone.js/testing'],
+  },
+): Promise<void> {
+  await silentNpm('install', 'jest@29.5.0', 'jest-environment-jsdom@29.5.0', '--save-dev');
+
+  await updateJsonFile('angular.json', (json) => {
+    const projects = Object.values(json['projects']);
+    if (projects.length !== 1) {
+      throw new Error(
+        `Expected exactly one project but found ${projects.length} projects named ${Object.keys(
+          json['projects'],
+        ).join(', ')}`,
+      );
+    }
+    const project = projects[0]! as any;
+
+    // Update to Jest builder.
+    const test = project['architect']['test'];
+    test['builder'] = '@angular-devkit/build-angular:jest';
+    test['options'] = options;
+  });
+}