han using the <code>MockUserService</code> directly, pass it through
 <a href="../retrofit/MockRestAdapter.html#create-java.lang.Class-T-"><code>the create method</code></a>.
 <pre>
   UserService service = mockRestAdapter.create(UserService.class, new MockUserService());
 </pre>
 The returned <code>UserService</code> instance will now behave like it is happening over the network
 while allowing the mock implementation to be written synchronously.
 <p>
 HTTP errors can be simulated in your mock services by 