Cleanup and starting to implements tracks.

src/workers/dispatcher-main.test.js

@@ -1,4 +1,4 @@
-import dispatch, { init, worker } from './dispatcher-main'
+import dispatch, { init, worker } from './dispatcher-main';
 
 jest.mock('./get-worker', () => ({
   getWorker: () => ({
@@ -21,8 +21,17 @@ describe('The dispatcher-main', () => {
   test('should return a promise if no callback is provided', () => {
     expect(dispatch('ping')).toBeInstanceOf(Promise);
   });
-  test('should send back the message', () => {
+  test('should forward the message', () => {
     dispatch('ping');
     expect(worker.port.postMessage).toBeCalledWith({ id: 0, payload: 'ping' });
   });
+  test('should return the response', () => {
+    var response;
+    const callback = (error, success) => {
+      response = success;
+    };
+    dispatch('ping', callback);
+    worker.port.onmessage({ data: { id: 0, payload: 'pong' } });
+    expect(response).toEqual('pong');
+  });
 });