@Test
public void whenGetAllWithEventIdValid() throws Exception {

    Event event = mock(Event.class);
    List<Registration> registrations = mock(List.class);
    when(eventEntityService.getById(TestConstants.EVENT_ID)).thenReturn(event);
    when(registrationEntityService.getAllWith(event)).thenReturn(registrations);
    List<Registration> actual = eventRegistrationService.getAllWithEventId(TestConstants.EVENT_ID);
    verify(eventEntityService).getById(TestConstants.EVENT_ID);
    verify(registrationEntityService).getAllWith(event);
    assertThat(actual).isSameAs(registrations);
}