我还发现：https://touk.pl/blog/2014/02/26/mock-retrofit-using-dagger-and-mockito/

在这里你会发现这个片段：

Unit Tests

During develop of app,you can send requests the server all time(or
most of time) so it is possible to live without mocked server,it
sucks but is possible. Unfortunately you are not able to write good
tests without the mock. Below there are two unit tests. Actually they
do not test anything but in simple way shows how to mock Retrofit
service using Mockito and Dagger.

@RunWith(RobolectricTestRunner.class)
public class EchoServiceTest {

    @Inject
    protected EchoService loginService;

    @Inject
    protected Client client;

    @Before
    public void setUp() throws Exception {
        Injector.add(new AndroidModule(),new RestServicesModule(),new RestServicesMockModule(),new TestModule());
        Injector.inject(this);
    }

    @Test
    public void shouldReturnOfferInAsyncMode() throws IOException {
        //given
        int expectedQuantity = 765;
        String responseContent = "{" +
                "   \"message\": \"mock message\"," +
                "   \"quantity\": \"" + expectedQuantity + "\"" +
                "}";
        mockResponseWithCodeAndContent(200,responseContent);

        //when
        EchoResponse echoResponse = loginService.getMessageAndQuantity("test","test");

        //then
        assertThat(echoResponse.getQuantity()).isEqualTo(expectedQuantity);
    }

    @Test
    public void shouldReturnOfferInAsyncModea() throws IOException {
        //given
        int expectedQuantity = 2;
        String responseContent = "{" +
                "   \"message\": \"mock message\","test");

        //then
        assertThat(echoResponse.getQuantity()).isEqualTo(expectedQuantity);
    }


    protected void mockResponseWithCodeAndContent(int httpCode,String content) throws IOException {
        Response response = createResponseWithCodeAndJson(httpCode,content);
        when(client.execute(Matchers.anyObject())).thenReturn(response);
    }

    private Response createResponseWithCodeAndJson(int responseCode,String json) {
        return new Response(responseCode,"nothing",Collections.EMPTY_LIST,new TypedByteArray("application/json",json.getBytes()));
    }

另请阅读：Square retrofit server mock for testing

希望它有所帮助