@Test
public void getRichMenuImageTest() throws Exception {

    whenCall(retrofitMock.getRichMenuImage(any()),
             ResponseBody.create(MediaType.parse("image/jpeg"), ZERO_BYTES));
    // Do
    final MessageContentResponse messageContentResponse = target.getRichMenuImage("ID").get();
    // Verify
    verify(retrofitMock, only()).getRichMenuImage("ID");
    assertThat(messageContentResponse.getLength()).isZero();
}