Web component test framework (wcTest.BrowserTest)

chrome/test/data/webui/web_component_test.js

Index: chrome/test/data/webui/web_component_test.js
diff --git a/chrome/test/data/webui/web_component_test.js b/chrome/test/data/webui/web_component_test.js
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+// Copyright 2015 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.
+
+/**
+ * @fileoverview Framework for running JavaScript tests of web components.
+ */
+
+// Namespace for web component tests.
+var wcTest = (function() {
+  /**
+   * @constructor
+   * @extends testing.Test
+   */
+  function BrowserTest() {}
+
+  BrowserTest.prototype = {
+    __proto__: testing.Test.prototype,
+
+    /**
+     * @override
+     * Navigate to the test WebUI.
+     */
+    browsePreload: 'chrome://web-component-test/',
+
+    /**
+     * The Mocha adapter assumes all tests are async.
+     * @override
+     * @final
+     */
+    isAsync: true,
+  };
+
+  /**
+   * Chains asynchronous functions to avoid nested setTimeouts.
+   * @return {Promise} A promise resolved after a minimal timeout.
+   */
+  function async() {
+    return new Promise(function(resolve, reject) {
+      setTimeout(resolve);
+    });
+  }
+
+  /**
+   * Removes all content from the body.
+   */
+  function clear() {
+    document.body.innerHTML = '';
+  }
+
+  /**
+   * Imports HTML using a <link> element.
+   * @param {string} uri The URI of the source to import.
+   * @return {Promise} A promise fulfilled when the link loads or errors out.
+   */
+  function importHtml(uri) {
+    var link = document.createElement('link');
+    link.rel = 'import';
+    link.href = uri;
+    document.head.appendChild(link);
+    return new Promise(function(resolve, reject) {
+      link.onload = function() {
+        resolve();
+      };
+      link.onerror = function() {
+        reject(new Error('Failed to import: ' + uri));
+      };
+    });
+  }
+
+  return {
+    BrowserTest: BrowserTest,
+    async: async,
+    clear: clear,
+    importHtml: importHtml,
+  };
+})();