test(@angular-devkit/build-angular): add browser builder statsJson option tests

This change adds expanded unit tests for the browser builder's `statsJson` option using the builder test harness.

Author: clydin

packages/angular_devkit/build_angular/src/browser/tests/options/stats-json_spec.ts

@@ -0,0 +1,77 @@
+/**
+ * @license
+ * Copyright Google Inc. 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.io/license
+ */
+import { buildWebpackBrowser } from '../../index';
+import { BASE_OPTIONS, BROWSER_BUILDER_INFO, describeBuilder } from '../setup';
+
+describeBuilder(buildWebpackBrowser, BROWSER_BUILDER_INFO, (harness) => {
+  describe('Option: "statsJson"', () => {
+    beforeEach(async () => {
+      // Application code is not needed for stat JSON tests
+      await harness.writeFile('src/main.ts', '');
+    });
+
+    it('generates a Webpack Stats file in output when true', async () => {
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        statsJson: true,
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+
+      if (harness.expectFile('dist/stats.json').toExist()) {
+        const content = harness.readFile('dist/stats.json');
+        expect(() => JSON.parse(content))
+          .withContext('Expected Webpack Stats file to be valid JSON.')
+          .not.toThrow();
+      }
+    });
+
+    it('includes Webpack profiling information', async () => {
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        statsJson: true,
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+
+      if (harness.expectFile('dist/stats.json').toExist()) {
+        const stats = JSON.parse(harness.readFile('dist/stats.json'));
+        expect(stats?.chunks?.[0]?.modules?.[0]?.profile?.building).toBeDefined();
+      }
+    });
+
+    it('does not generate a Webpack Stats file in output when false', async () => {
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        statsJson: false,
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+
+      harness.expectFile('dist/stats.json').toNotExist();
+    });
+
+    it('does not generate a Webpack Stats file in output when not present', async () => {
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+
+      harness.expectFile('dist/stats.json').toNotExist();
+    });
+  });
+});