Adding first unit tests with mocks

chrome/browser/resources/google_now/background_test_util.js

Index: chrome/browser/resources/google_now/background_test_util.js
diff --git a/chrome/browser/resources/google_now/background_test_util.js b/chrome/browser/resources/google_now/background_test_util.js
index f59c34ed15c2f8198e9bc28ee0d921ddce174f23..dca512e4e4cd5957e8c7ba3f6b397bc91acbfaad 100644
--- a/chrome/browser/resources/google_now/background_test_util.js
+++ b/chrome/browser/resources/google_now/background_test_util.js
@@ -22,4 +22,63 @@ chrome['runtime'] = {
   onInstalled: emptyListener,
   onStartup: emptyListener
 };
+
 var storage = {};
+
+/**
+ * Syntactic sugar for use with will() on a Mock4JS.Mock.
+ * Creates an action for will() that invokes a callback that the tested code
+ * passes to a mocked function.
+ * @param {SaveMockArguments} savedArgs Arguments that will contain the
+ *     callback once the mocked function is called.
+ * @param {number} callbackParameter Index of the callback parameter in
+ *     |savedArgs|.
+ * @param {...Object} var_args Arguments to pass to the callback.
+ * @return {CallFunctionAction} Action for use in will().
+ */
+function invokeCallback(savedArgs, callbackParameter, var_args) {
+  var callbackArguments = Array.prototype.slice.call(arguments, 2);
+  return callFunction(function() {
+    savedArgs.arguments[callbackParameter].apply(null, callbackArguments);
+  });
+}
+
+/**
+  * Mock4JS matcher object that matches the actual agrument and the expected
+  * value iff their JSON represenations are same.
+  * @param {Object} expectedValue Expected value.
+  * @constructor
+  */
+function MatchJSON(expectedValue) {
+  this.expectedValue_ = expectedValue;
+}
+
+MatchJSON.prototype = {
+  /**
+    * Checks that JSON represenation of the actual and expected arguments are
+    * same.
+    * @param {Object} actualArgument The argument to match.
+    * @return {boolean} Result of the comparison.
+    */
+  argumentMatches: function(actualArgument) {
+    return JSON.stringify(this.expectedValue_) ===
+        JSON.stringify(actualArgument);
+  },
+
+  /**
+    * Describes the matcher.
+    * @return {string} Description of this Mock4JS matcher.
+    */
+  describe: function() {
+    return 'eqJSON(' + JSON.stringify(this.expectedValue_) + ')';
+  }
+};
+
+/**
+  * Builds a MatchJSON agrument matcher for a given expected value.
+  * @param {Object} expectedValue Expected value.
+  * @return {MatchJSON} Resulting Mock4JS matcher.
+  */
+function eqJSON(expectedValue) {
+  return new MatchJSON(expectedValue);
+}