Angular, Karma/Jasmine/Chai/Sinon testing of a provider

I am having a bit of an issue testing an object constructor in a provider I have set up here. It lets users set up objects in their .config so I can then reference them later to check validity of requested objects (keeps a reference for checking as a short answer).

So I have it all set up and working great, however I'm trying to get some unit testing integrated with this and am running into some trouble.

So I pulled out the guts of the functions (they wont really help here) and here's what I have :

 $moduleObjectProvider.$inject = [];

     function $moduleObjectProvider() {

         var currentModules = {};

         //outer closure to inject "this"
         function outerAddState(moduleObj) {
             return function(stateName, stateOptions) {       
                //extend currentModules with verified state/module;
         }

         //outer function so we can push into module (closure)
         function modulePush(currentModule, name) {
             var tempMod = {};
             tempMod[name] = currentModule;
             _.extend(currentModules, tempMod);
         }

         this.$get = $get;

         $get.$inject = ['URLfactory', '$log', '$location'];

         function $get(URLfactory, $log, $location) {

             return {
                 goState: function(name, stateName, options) {
                     if (currentModules[name]) {
                         this.prepState(name, stateName, options);
                     } else {
                     }
                 },
                 prepState: function(name, stateName, options) {
                     if (currentModules[name].states[stateName]) {
                        //
                     } else {
                         //throw error
                         $log.error("Requested Module exists, but state does not.");
                     }
                 },
                 moduleConstructor: function(name, cb) {
                     if (currentModules[name]) {
                         //throw error
                         $log.warn(name + " module already exists.");
                     } else {
                         this.states = [];
                         this.callback = cb;
                         this.addState = outerAddState(this);
                         modulePush(this, name);

                     }
                 },
                 modules: function() {
                     return currentModules;
                 }
             };
         }
     }

     angular.module(metadata.moduleName, []).provider(metadata.componentName, $moduleObjectProvider);

Excuse the require.js naming convention. So this is owrking great, however where I am having trouble is testing the prepState() and goState() functions. This is mostly because they reference the currentModules object. I can push a module into it but I cannot seem to get the addstate functions to fire correctly within the unit tests.

So in the normal scenario, in the .config (with this provider injected) I can just do something like this -

  new ($moduleObjectProvider.$get()).moduleConstructor("module1", callback)
            .addState("newState", ["day", "week", "month"]);

This pushes in a new module and it's states. However in the unit test I have only gotten this far (inside a test) -

                var callback = function(a, b) {};
                URLprovider.moduleConstructor("module1", callback);

So, this works fine for JUST pushing the module in, but in order to test prepstate and gostate, i need to push the states inside too, the .addState("newState", ["day", "week", "month"]); chain in the running code.

However I cannot seem to chain, if I try

  URLprovider.moduleConstructor("module1", callback).addState("newState", ["day", "week", "month"]); 

(just trying chaining onto the working "add just module" part) I get -

  TypeError: 'undefined' is not an object (evaluating 'URLprovider.moduleConstructor("module1", callback).addState')

I'm thinking it may be because the this.addState calls a closure function outside of the $get maybe? Is there some way around this, or am I doing this incorrectly? Any insight would be might appreciated, thanks!