[Core] Add test case for shared listener

Add test case for sharing listeners across mutation
capability instances, WTD-1329.

platform/core/src/capabilities/MutationCapability.js

@@ -29,6 +29,8 @@ define(
     function () {
         "use strict";
 
+        var TOPIC_PREFIX = "mutation:";
+
         // Utility function to overwrite a destination object
         // with the contents of a source object.
         function copyValues(destination, source) {
@@ -72,13 +74,7 @@ define(
          * @constructor
          */
         function MutationCapability(topic, now, domainObject) {
-            var listeners = [];
+            var t = topic(TOPIC_PREFIX + domainObject.getId());
-
-            function notifyListeners(model) {
-                listeners.forEach(function (listener) {
-                    listener(model);
-                });
-            }
 
             function mutate(mutator, timestamp) {
                 // Get the object's model and clone it, so the
@@ -103,7 +99,7 @@ define(
                             copyValues(model, result);
                         }
                         model.modified = useTimestamp ? timestamp : now();
-                        notifyListeners(model);
+                        t.notify(model);
                     }
 
                     // Report the result of the mutation
@@ -116,12 +112,7 @@ define(
             }
 
             function listen(listener) {
-                listeners.push(listener);
+                return t.listen(listener);
-                return function unlisten() {
-                    listeners = listeners.filter(function (l) {
-                        return l !== listener;
-                    });
-                };
             }
 
             return {

platform/core/test/capabilities/MutationCapabilitySpec.js

@@ -36,7 +36,10 @@ define(
             var testModel,
                 topic,
                 mockNow,
-                domainObject = { getModel: function () { return testModel; } },
+                domainObject = {
+                    getId: function () { return "test-id"; },
+                    getModel: function () { return testModel; }
+                },
                 mutation;
 
             beforeEach(function () {
@@ -112,6 +115,22 @@ define(
                 });
                 expect(mockCallback).not.toHaveBeenCalled();
             });
+
+            it("shares listeners across instances", function () {
+                var mockCallback = jasmine.createSpy('callback'),
+                    otherMutation = new MutationCapability(
+                        topic,
+                        mockNow,
+                        domainObject
+                    );
+                mutation.listen(mockCallback);
+                otherMutation.invoke(function (m) {
+                    m.number = 8;
+                });
+                expect(mockCallback).toHaveBeenCalled();
+                expect(mockCallback.mostRecentCall.args[0].number)
+                    .toEqual(8);
+            });
         });
     }
 );