MD Settings: reduce complexity and overhead of prefs singleton

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 settings-prefs. */
 cr.define('settings_prefs', function() {
   /**
    * Creates a deep copy of the object.
    * @param {!Object} obj
    * @return {!Object}
    */
   function deepCopy(obj) {
     return JSON.parse(JSON.stringify(obj));
   }
 
   function registerTests() {
     suite('CrSettingsPrefs', function() {
       /**
        * Prefs instance created before each test.
-       * @type {CrSettingsPrefsElement|undefined}
+       * @type {SettingsPrefsElement|undefined}
        */
       var prefs;
 
       /** @type {settings.FakeSettingsPrivate} */
       var fakeApi = null;
 
       /**
        * @param {!Object} prefStore Pref store from <settings-prefs>.
        * @param {string} key Pref key of the pref to return.
        * @return {chrome.settingsPrivate.PrefObject|undefined}
@@ skipping 32 matching lines @@
       function assertPrefsSet(testCaseValueIndex) {
         for (var testCase of prefsTestCases) {
           var expectedValue = JSON.stringify(
               testCase.nextValues[testCaseValueIndex]);
           var actualValue = JSON.stringify(
               prefs.get('prefs.' + testCase.pref.key + '.value'));
           assertEquals(expectedValue, actualValue);
         }
       }
 
-      /**
-       * List of CrSettingsPref elements created for testing.
-       * @type {!Array<!CrSettingsPrefs>}
-       */
-      var createdElements = [];
-
-      // Initialize <settings-prefs> elements before each test.
+      // Initialize a <settings-prefs> before each test.
       setup(function() {
         // Override chrome.settingsPrivate with FakeSettingsPrivate.
         fakeApi = new settings.FakeSettingsPrivate(
             prefsTestCases.map(function(testCase) {
               return testCase.pref;
             }));
         CrSettingsPrefs.deferInitialization = true;
 
-        // Create and attach the <settings-prefs> elements. Make several of
-        // them to test that the shared state model scales correctly.
-        createdElements = [];
-        for (var i = 0; i < 100; i++) {
-          var prefsInstance = document.createElement('settings-prefs');
-          document.body.appendChild(prefsInstance);
-          createdElements.push(prefsInstance);
-          prefsInstance.initializeForTesting(fakeApi);
-        }
-        // 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];
+        prefs = document.createElement('settings-prefs');
+        prefs.initialize(fakeApi);
 
         // getAllPrefs is asynchronous, so return the prefs promise.
         return CrSettingsPrefs.initialized;
       });
 
       teardown(function() {
         CrSettingsPrefs.resetForTesting();
         CrSettingsPrefs.deferInitialization = false;
-
-        // Reset each <settings-prefs>. TODO(michaelpg): make settings-prefs
-        // less dependent on testing state so we don't have to do this.
-        for (var i = 0; i < createdElements.length; i++)
-          createdElements[i].resetForTesting();
+        prefs.resetForTesting();
 
         PolymerTest.clearBody();
       });
 
       test('receives and caches prefs', function testGetPrefs() {
         // Test that each pref has been successfully copied to the Polymer
         // |prefs| property.
         for (var key in fakeApi.prefs) {
           var expectedPref = fakeApi.prefs[key];
           var actualPref = getPrefFromKey(prefs.prefs, key);
@@ skipping 63 matching lines @@
         fakeApi.sendPrefChanges(prefChanges);
         assertPrefsSet(1);
       });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });