MD-Settings: convert cr-settings-prefs to a singleton model

chrome/test/data/webui/settings/prefs_tests.js

 // 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 Suite of tests for cr-settings-prefs. */
 cr.define('cr_settings_prefs', function() {
   /**
    * Creates a deep copy of the object.
    * @param {!Object} obj
    * @return {!Object}
    */
   function deepCopy(obj) {
     return JSON.parse(JSON.stringify(obj));
   }
 
   /**
    * Mock of chrome.settingsPrivate API.
    * @constructor
    * @extends {chrome.settingsPrivate}
    */
   function MockSettingsApi() {
     this.prefs = {};
-    this.listener_ = null;
 
     // Hack alert: bind this instance's onPrefsChanged members to this.
     this.onPrefsChanged = {
       addListener: this.onPrefsChanged.addListener.bind(this),
       removeListener: this.onPrefsChanged.removeListener.bind(this),
     };
 
     for (var testCase of prefsTestCases)
       this.addPref_(testCase.type, testCase.key, testCase.values[0]);
   }
 
+  // Make the listener static because it refers to a singleton.
+  MockSettingsApi.listener_ = null;
+
   MockSettingsApi.prototype = {
     // chrome.settingsPrivate overrides.
     onPrefsChanged: {
       addListener: function(listener) {
-        this.listener_ = listener;
+        MockSettingsApi.listener_ = listener;
       },
 
       removeListener: function(listener) {
-        expectNotEquals(null, this.listener_);
-        this.listener_ = null;
+        assertNotEquals(null, MockSettingsApi.listener_);

[michaelpg, 2015/09/20 21:01:56]

Switched expects to asserts because test_api.js makes it hard to determine what
test failed when an expect fails.

Also, a failure is likely to involve all prefs, making the log spew is too high
for expects.

+        MockSettingsApi.listener_ = null;
       },
     },
 
     getAllPrefs: function(callback) {
       // Send a copy of prefs to keep our internal state private.
       var prefs = [];
       for (var key in this.prefs)
         prefs.push(deepCopy(this.prefs[key]));
 
-      callback(prefs);
+      // Run the callback asynchronously to test that the prefs aren't actually
+      // used before they become available.
+      setTimeout(callback.bind(null, prefs));
     },
 
     setPref: function(key, value, pageId, callback) {
       var pref = this.prefs[key];
       assertNotEquals(undefined, pref);
       assertEquals(typeof value, typeof pref.value);
       assertEquals(Array.isArray(value), Array.isArray(pref.value));
 
       if (this.failNextSetPref_) {
         callback(false);
@@ skipping 38 matching lines @@
      * @param {!Object<{key: string, value: *}>} changes
      */
     sendPrefChanges: function(changes) {
       var prefs = [];
       for (var change of changes) {
         var pref = this.prefs[change.key];
         assertNotEquals(undefined, pref);
         pref.value = change.value;
         prefs.push(deepCopy(pref));
       }
-      this.listener_(prefs);
+      MockSettingsApi.listener_(prefs);
     },
 
     // Private methods for use by the mock API.
 
     /**
      * @param {!chrome.settingsPrivate.PrefType} type
      * @param {string} key
      * @param {*} value
      */
     addPref_: function(type, key, value) {
@@ skipping 30 matching lines @@
             return undefined;
         }
         return pref;
       }
 
       /**
        * Checks that the mock API pref store contains the expected values.
        * @param {number} testCaseValueIndex The index of possible values from
        *     the test case to check.
        */
-      function expectMockApiPrefsSet(testCaseValueIndex) {
+      function assertMockApiPrefsSet(testCaseValueIndex) {
         for (var testCase of prefsTestCases) {
           var expectedValue = JSON.stringify(
               testCase.values[testCaseValueIndex]);
           var actualValue = JSON.stringify(mockApi.prefs[testCase.key].value);
-          expectEquals(expectedValue, actualValue);
+          assertEquals(expectedValue, actualValue);
         }
       }
 
       /**
        * Checks that the <cr-settings-prefs> contains the expected values.
        * @param {number} testCaseValueIndex The index of possible values from
        *     the test case to check.
        */
-      function expectPrefsSet(testCaseValueIndex) {
+      function assertPrefsSet(testCaseValueIndex) {
         for (var testCase of prefsTestCases) {
           var expectedValue = JSON.stringify(
               testCase.values[testCaseValueIndex]);
           var actualValue = JSON.stringify(
               prefs.get('prefs.' + testCase.key + '.value'));
-          expectEquals(expectedValue, actualValue);
+          assertEquals(expectedValue, actualValue);
         }
       }
 
-      // Initialize a <cr-settings-prefs> element before each test.
-      setup(function(done) {
+      /**
+       * List of CrSettingsPref elements created for testing.
+       * @type {!Array<!CrSettingsPrefs>}
+       */
+      var createdElements = [];
+
+      // Initialize <cr-settings-prefs> elements before each test.
+      setup(function() {
         mockApi = new MockSettingsApi();
         // TODO(michaelpg): don't use global variables to inject the API.
         window.mockApi = mockApi;
 
-        // Create and attach the <cr-settings-prefs> element.
+        // Create and attach the <cr-settings-prefs> elements. Make several of
+        // them to test that the shared state model scales correctly.
+        createdElements = [];
+        for (var i = 0; i < 200; i++) {
+          var prefsInstance = document.createElement('cr-settings-prefs');
+          document.body.appendChild(prefsInstance);
+          createdElements.push(prefsInstance);
+        }
+        // For simplicity, only use one prefs element in the tests. Use an
+        // arbitrary index instead of the first or last element created.
+        prefs = createdElements[42];
+
+        // getAllPrefs is asynchronous, so return the prefs promise.
+        return CrSettingsPrefs.initialized;
+      });
+
+      teardown(function() {
+        CrSettingsPrefs.reset();
+
+        // Reset each <cr-settings-prefs>.
+        for (var i = 0; i < createdElements.length; i++)
+          createdElements[i].resetForTesting();
+
         PolymerTest.clearBody();
-        prefs = document.createElement('cr-settings-prefs');
-        document.body.appendChild(prefs);
-
         window.mockApi = undefined;
-
-        // Wait for CrSettingsPrefs.INITIALIZED.
-        if (!CrSettingsPrefs.isInitialized) {
-          var listener = function() {
-            document.removeEventListener(CrSettingsPrefs.INITIALIZED, listener);
-            done();
-          };
-          document.addEventListener(CrSettingsPrefs.INITIALIZED, listener);
-          return;
-        }
-
-        done();
       });
 
       test('receives and caches prefs', function() {
         // Test that each pref has been successfully copied to the Polymer
         // |prefs| property.
         for (var key in mockApi.prefs) {
           var expectedPref = mockApi.prefs[key];
           var actualPref = getPrefFromKey(prefs.prefs, key);
           if (!expectNotEquals(undefined, actualPref)) {
             // We've already registered an error, so skip the pref.
             continue;
           }
 
-          expectEquals(JSON.stringify(expectedPref),
+          assertEquals(JSON.stringify(expectedPref),
                        JSON.stringify(actualPref));
         }
       });
 
       test('forwards pref changes to API', function() {
         // Test that cr-settings-prefs uses the setPref API.
         for (var testCase of prefsTestCases) {
           prefs.set('prefs.' + testCase.key + '.value',
                     deepCopy(testCase.values[1]));
         }
         // Check that setPref has been called for the right values.
-        expectMockApiPrefsSet(1);
+        assertMockApiPrefsSet(1);
 
         // Test that when setPref fails, the pref is reverted locally.
         for (var testCase of prefsTestCases) {
           mockApi.failNextSetPref();
           prefs.set('prefs.' + testCase.key + '.value',
                     deepCopy(testCase.values[2]));
         }
 
-        expectPrefsSet(1);
+        assertPrefsSet(1);
 
         // Test that setPref is not called when the pref doesn't change.
         mockApi.disallowSetPref();
         for (var testCase of prefsTestCases) {
           prefs.set('prefs.' + testCase.key + '.value',
                     deepCopy(testCase.values[1]));
         }
-        expectMockApiPrefsSet(1);
+        assertMockApiPrefsSet(1);
         mockApi.allowSetPref();
       });
 
       test('responds to API changes', function() {
         // Changes from the API should not result in those changes being sent
         // back to the API, as this could trigger a race condition.
         mockApi.disallowSetPref();
         var prefChanges = [];
         for (var testCase of prefsTestCases)
           prefChanges.push({key: testCase.key, value: testCase.values[1]});
 
         // Send a set of changes.
         mockApi.sendPrefChanges(prefChanges);
-        expectPrefsSet(1);
+        assertPrefsSet(1);
 
         prefChanges = [];
         for (var testCase of prefsTestCases)
           prefChanges.push({key: testCase.key, value: testCase.values[2]});
 
         // Send a second set of changes.
         mockApi.sendPrefChanges(prefChanges);
-        expectPrefsSet(2);
+        assertPrefsSet(2);
 
         // Send the same set of changes again -- nothing should happen.
         mockApi.sendPrefChanges(prefChanges);
-        expectPrefsSet(2);
+        assertPrefsSet(2);
       });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });