@Test
public void validateSingleness_personAlreadyRegistered() {
when(repository.findByContactEmail(PERSONS_EMAIL)).thenReturn(Optional.of(person));
exception.expect(PersonAlreadyRegisteredException.class);
subject.execute(person);
}
private void configureRepository() {
when(repository.findByContactEmail(PERSONS_EMAIL)).thenReturn(Optional.ofNullable(null));
}