### Question:
TaxTransferer { public void transferTaxFor(Person person) { if (person == null) { return; } taxService.transferTaxFor(person); } TaxTransferer(TaxService taxService); void transferTaxFor(Person person);  }### Answer:
@Test public void should_not_call_web_service_method_if_person_is_null() { systemUnderTest.transferTaxFor(null); verify(taxService, never()).transferTaxFor(any(Person.class)); }
@Test public void should_not_interact_with_web_service_in_any_way_if_person_is_null() { systemUnderTest.transferTaxFor(null); verifyZeroInteractions(taxService); }