[ntp] Add tests for ModuleDescriptor

Tests ModuleDescriptor.initialize, which is the only function of that
class with non-trivial logic. Adding tests is a precursor to making
changes to that class in subsequent CLs.

Change-Id: Ib023f014f21e547bcbf38776781a95b6d83b3e2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2623653
Auto-Submit: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842396}

chrome/test/data/webui/new_tab_page/modules/module_descriptor_test.js

+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import {BrowserProxy, ModuleDescriptor} from 'chrome://new-tab-page/new_tab_page.js';
+import {createTestProxy} from 'chrome://test/new_tab_page/test_support.js';
+
+suite('NewTabPageModulesModuleDescriptorTest', () => {
+  /**
+   * @implements {BrowserProxy}
+   * @extends {TestBrowserProxy}
+   */
+  let testProxy;
+
+  setup(() => {
+    PolymerTest.clearBody();
+    testProxy = createTestProxy();
+    BrowserProxy.instance_ = testProxy;
+  });
+
+  test('instantiate module with data', async () => {
+    // Arrange.
+    const element = document.createElement('div');
+    const moduleDescriptor =
+        new ModuleDescriptor('foo', 100, () => Promise.resolve(element));
+    testProxy.setResultFor('now', 123);
+
+    // Act.
+    await moduleDescriptor.initialize();
+
+    // Assert.
+    assertEquals(element, moduleDescriptor.element);
+    const [id, now] = await testProxy.handler.whenCalled('onModuleLoaded');
+    assertEquals(1, testProxy.handler.getCallCount('onModuleLoaded'));
+    assertEquals('foo', id);
+    assertEquals(123, now);
+  });
+
+  test('instantiate module without data', async () => {
+    // Arrange.
+    const moduleDescriptor =
+        new ModuleDescriptor('foo', 100, () => Promise.resolve(null));
+
+    // Act.
+    await moduleDescriptor.initialize();
+
+    // Assert.
+    assertEquals(null, moduleDescriptor.element);
+    assertEquals(0, testProxy.handler.getCallCount('onModuleLoaded'));
+  });
+});

chrome/test/data/webui/new_tab_page/new_tab_page_browsertest.js

@@ -195,6 +195,19 @@ TEST_F('NewTabPageImgTest', 'All', function() {
   mocha.run();
 });
 
+// eslint-disable-next-line no-var
+var NewTabPageModulesModuleDescriptorTest =
+    class extends NewTabPageBrowserTest {
+  /** @override */
+  get browsePreload() {
+    return 'chrome://new-tab-page/test_loader.html?module=new_tab_page/modules/module_descriptor_test.js';
+  }
+};
+
+TEST_F('NewTabPageModulesModuleDescriptorTest', 'All', function() {
+  mocha.run();
+});
+
 // eslint-disable-next-line no-var
 var NewTabPageModulesModuleRegistryTest = class extends NewTabPageBrowserTest {
   /** @override */