### Question:
TaxTransferer { public void transferTaxFor(Person person) { if (person == null) { taxService.sendErrorReport(); return; } taxService.transferTaxFor(person); } TaxTransferer(TaxService taxService); void transferTaxFor(Person person);  }### Answer:
@Test public void should_only_send_error_report_if_person_is_null() throws Exception { systemUnderTest.transferTaxFor(null); verify(taxService, only()).sendErrorReport(); }
@Test public void should_only_send_error_report_if_person_is_null_in_an_ugly_way() throws Exception { systemUnderTest.transferTaxFor(null); verify(taxService).sendErrorReport(); verifyNoMoreInteractions(taxService); }