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

MainActivityTest.java

    @Test
    public void testGoodAnswer() throws Exception {
        RESTMockServer.whenGET(RequestMatchers.pathEndsWith("users/andrzejchm")).thenReturnFile(
                "users/andrzejchm.json");
        //launches activity with default intent
        rule.launchActivity(null);
        pageObject.typeUsername("andrzejchm");
        pageObject.pressOk();
        pageObject.verifyWelcomeMessageForUser("Welcome Andrzej Chmielewski!");
    }