Make socket.on/socket.addListener chainable

mock/socket-io.js

@@ -7,10 +7,12 @@ function createMockSocketObject () {
   var socket = {
     on: function (ev, fn) {
       (this._listeners[ev] = this._listeners[ev] || []).push(fn);
+      return this;
     },
     once: function (ev, fn) {
       (this._listeners[ev] = this._listeners[ev] || []).push(fn);
       fn._once = true;
+      return this;
     },
     emit: function (ev, data) {
       if (this._listeners[ev]) {

socket.js

@@ -33,11 +33,11 @@ angular.module('btford.socket-io', []).
         var defaultScope = options.scope || $rootScope;
 
         var addListener = function (eventName, callback) {
-          socket.on(eventName, callback.__ng = asyncAngularify(socket, callback));
+          return socket.on(eventName, callback.__ng = asyncAngularify(socket, callback));
         };
 
         var addOnceListener = function (eventName, callback) {
-          socket.once(eventName, callback.__ng = asyncAngularify(socket, callback));
+          return socket.once(eventName, callback.__ng = asyncAngularify(socket, callback));
         };
 
         var wrappedSocket = {

socket.spec.js

@@ -44,6 +44,21 @@ describe('socketFactory', function () {
       expect(spy).toHaveBeenCalled();
     });
 
+    it('should add listeners in chain', function () {
+      var counter = 0,
+          func = function () {
+            counter += 1;
+          };
+
+      socket.on('event1', func)
+            .on('event2', func);
+
+      mockIoSocket.emit('event1');
+      mockIoSocket.emit('event2');
+      $timeout.flush();
+
+      expect(counter).toBe(2);
+    });
   });