@Test
public void whenAddValid() throws Exception {

    RegistrationAddPayload registrationAddPayload = new RegistrationAddPayload();
    registrationAddPayload.setEventId(TestConstants.EVENT_ID);
    Registration registration = mock(Registration.class);
    when(registrationEntityService.add(registrationAddPayload)).thenReturn(registration);
    Registration actual = eventRegistrationService.add(registrationAddPayload);
    verify(eventEntityService).getById(TestConstants.EVENT_ID);
    verify(registrationEntityService).add(registrationAddPayload);
    assertThat(actual).isSameAs(registration);
}