https://medium.com/@andrzejchm/ittd-instrumentation-ttd-for-android-4894cbb82d37#.nk6hnm2jh

MainActivityTest.java

    @Test
    public void testPlayground() throws Exception {
        RESTMockServer.whenGET(RequestMatchers.pathEndsWith("users/andrzejchm")).thenReturnFile(
                "users/andrzejchm.json");
        //launches activity with default intent
        rule.launchActivity(null);
        Thread.sleep(10000);
    }