test(@angular-devkit/build-angular): add dev-server builder publicHost option

This change adds expanded unit tests for the dev-server builder's `publicHost` option using the builder test harness.

Author: clydin

packages/angular_devkit/build_angular/src/dev-server/public-host_spec.ts

@@ -0,0 +1,69 @@
+/**
+ * @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 { serveWebpackBrowser } from '../../index';
+import { executeOnceAndFetch } from '../execute-fetch';
+import {
+  BASE_OPTIONS,
+  DEV_SERVER_BUILDER_INFO,
+  describeBuilder,
+  setupBrowserTarget,
+} from '../setup';
+
+const FETCH_HEADERS = Object.freeze({ host: 'example.com' });
+
+describeBuilder(serveWebpackBrowser, DEV_SERVER_BUILDER_INFO, (harness) => {
+  describe('option: "publicHost"', () => {
+    beforeEach(async () => {
+      setupBrowserTarget(harness);
+
+      // Application code is not needed for these tests
+      await harness.writeFile('src/main.ts', '');
+    });
+
+    it('does not allow an invalid host when option is not present', async () => {
+      harness.useTarget('serve', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result, response } = await executeOnceAndFetch(harness, '/', {
+        request: { headers: FETCH_HEADERS },
+      });
+
+      expect(result?.success).toBeTrue();
+      expect(await response?.text()).toBe('Invalid Host header');
+    });
+
+    it('does not allow an invalid host when option is a different host', async () => {
+      harness.useTarget('serve', {
+        ...BASE_OPTIONS,
+        publicHost: 'example.net',
+      });
+
+      const { result, response } = await executeOnceAndFetch(harness, '/', {
+        request: { headers: FETCH_HEADERS },
+      });
+
+      expect(result?.success).toBeTrue();
+      expect(await response?.text()).toBe('Invalid Host header');
+    });
+
+    it('allows a host when option is set to used host', async () => {
+      harness.useTarget('serve', {
+        ...BASE_OPTIONS,
+        publicHost: 'example.com',
+      });
+
+      const { result, response } = await executeOnceAndFetch(harness, '/', {
+        request: { headers: FETCH_HEADERS },
+      });
+
+      expect(result?.success).toBeTrue();
+      expect(await response?.text()).toContain('<title>');
+    });
+  });
+});