@Test
public void getGroupMemberCount() throws Exception {

    GroupMemberCountResponse dummyResponse = GroupMemberCountResponse
            .builder()
            .count(3L)
            .build();
    whenCall(retrofitMock.getGroupMemberCount(any()),
             dummyResponse);
    // Do
    GroupMemberCountResponse got = target.getGroupMemberCount("GGGGGGGGGGGGGGGGGG")
                                         .get();
    // Verify
    verify(retrofitMock, only()).getGroupMemberCount("GGGGGGGGGGGGGGGGGG");
    assertThat(got).isEqualTo(dummyResponse);
}