2부 - Mockito

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-core</artifactId>
    <version>3.1.0</version>
    <scope>test</scope>
</dependency>


<-- Mockito Jupiter - JUnit과 Mockito의 연동 (JUnit의 Extention임) -->
<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-junit-jupiter</artifactId>
    <version>3.1.0</version>
    <scope>test</scope>
</dependency>

Mock을 활용한 테스트를 작성하는법

• Mock을 만드는 방법

• Mock의 동작을 관리하는 방법

• Mock의 행동을 검증하는 방법

1. Mock을 만드는 방법

MemberService memberService = Mockito.mock(MemberService.class);
StudyRepository studyRepository = Mockito.(StudyRepository.class);

1. @Mock 어노테이션 활용

• 클래스에 @ExtendWith(MockitoExtension.class) 있어야함

@Mock MemberService memberService;
@Mock StudyRepository studyRepository;

@Test
void createStudyService(@Mock MemberService memberService,
                        @Mock StudyRepository studyRepository) {
    ...
}

1. Mock Object Stubbing

• null을 return

• Optional 타입은 Optional.empty

• primitive 타입은 기본 primitive 값

• collection은 빈 콜렉션

• void 를 리턴하는 메소드는 예외를 던지지 않고 아무것도 하지 않음

@Test
    void createNewStudy(@Mock MemberService memberService,
                            @Mock StudyRepository studyRepository) {
        StudyService studyService = new StudyService(memberService, studyRepository);
        assertNotNull(studyService);

        Member member = new Member();
        member.setId(1L);
        member.setEmail("keesun@email.com");

        Mockito.when(memberService.findById(ArgumentMatchers.any()))
                .thenReturn(Optional.of(member))
                .thenThrow(new RuntimeException())
                .thenReturn(Optional.empty());

        Optional<Member> byId = memberService.findById(1L);
        assertEquals("keesun@email.com", byId.get().getEmail());

        assertThrows(RuntimeException.class, () -> {
            memberService.findById(2L);
        });

        assertEquals(Optional.empty(), memberService.findById(3L));
    }