ArgumentCaptor

1-controller-method.java

public String processFindForm(Owner owner, BindingResult result, Model model){
    // allow parameterless GET request for /owners to return all records
    if (owner.getLastName() == null) {
        owner.setLastName(""); // empty string signifies broadest possible search
    }

    // find owners by last name
    List<Owner> results = ownerService.findAllByLastNameLike("%"+ owner.getLastName() + "%");

    if (results.isEmpty()) {
        // no owners found
        result.rejectValue("lastName", "notFound", "not found");
        return "owners/findOwners";
    } else if (results.size() == 1) {
        // 1 owner found
        owner = results.get(0);
        return "redirect:/owners/" + owner.getId();
    } else {
        // multiple owners found
        model.addAttribute("selections", results);
        return "owners/ownersList";
    }
}

2-argument-captor-ex.java

@Test
void testProcessFindForm() {
  // given
  Owner owner = new Owner(1l, "Shin", "Daewook");
  List<Owner> owners = new ArrayList<>();
  final ArgumentCaptor<String> captor = ArgumentCaptor.forClass(String.class);
  given(ownerService.findAllByLastNameLike(captor.capture())).willReturn(owners);

  // when
  String result = ownerController.processFindForm(owner, bindingResult, null);

  // then
  assertThat("%Daewook%").isEqualToIgnoringCase(captor.getValue());
}

3-argument-captor-ex.java

@Captor
ArgumentCaptor<String> stringArgumentCaptor;

@Test
void testProcessFindFormAnnotation() {
  // given
  Owner owner = new Owner(1l, "Shin", "Daewook");
  List<Owner> owners = new ArrayList<>();
  final ArgumentCaptor<String> captor = ArgumentCaptor.forClass(String.class);
  given(ownerService.findAllByLastNameLike(stringArgumentCaptor.capture())).willReturn(owners);

  // when
  String result = ownerController.processFindForm(owner, bindingResult, null);

  // then
  assertThat("%Daewook%").isEqualToIgnoringCase(stringArgumentCaptor.getValue());
}

ArgumentCaptor을 사용하여 특정 메소드에 사용되는 아규먼트를 capture(저장) 해놓았다가 나중에 다시 사용(getValue)할 수 있다. 아큐먼트의 값(혹은 객체) 에 대해서도 테스트를 진행하기 위해 사용한다.

Argument Matcher와 다른 점은 따로 클래스를 만들 필요가 없다는 점, 그리고 verification에만 사용할 수 있다는 점이다.