@Test
public void getMessageContentTest() throws Exception {

    whenCall(retrofitMock.getMessageContent(any()),
             ResponseBody.create(MediaType.parse("image/jpeg"), ZERO_BYTES));
    // Do
    final MessageContentResponse contentResponse = target.getMessageContent("ID").get();
    // Verify
    verify(retrofitMock, only()).getMessageContent("ID");
    assertThat(contentResponse.getLength()).isEqualTo(0);
    assertThat(contentResponse.getMimeType()).isEqualTo("image/jpeg");
}