majiayu000 Spring Boot TDD with Mockito
TDD Cycle: Red → Green → Refactor
┌─────────────────────────────────────────────────────────────┐
│ TDD WORKFLOW │
│ │
│ ┌───────┐ ┌───────┐ ┌──────────┐ │
│ │ RED │ ───→ │ GREEN │ ───→ │ REFACTOR │ ───┐ │
│ │ │ │ │ │ │ │ │
│ │ Write │ │ Write │ │ Improve │ │ │
│ │ Test │ │ Code │ │ Code │ │ │
│ └───────┘ └───────┘ └──────────┘ │ │
│ ↑ │ │
│ └──────────────────────────────────────────┘ │
└─────────────────────────────────────────────────────────────┘
Mockito Annotations
| Annotation | Purpose |
|---|---|
@Mock |
Create mock object |
@InjectMocks |
Inject mocks into class under test |
@Spy |
Partial mock - real methods + mock behavior |
@Captor |
Capture arguments passed to mock |
@MockBean |
Mock bean in Spring context |
Test Template
@ExtendWith(MockitoExtension.class)
class ServiceTest {
@Mock
private Repository repository;
@InjectMocks
private Service service;
@Test
@DisplayName("Should do something when condition is met")
void shouldDoSomethingWhenConditionIsMet() {
// Given (Arrange)
when(repository.findById(1L)).thenReturn(Optional.of(entity));
// When (Act)
var result = service.doSomething(1L);
// Then (Assert)
assertThat(result).isNotNull();
verify(repository).findById(1L);
}
}
Best Practices
- One assertion per test - Focus on single behavior
- Descriptive test names - Use
@DisplayName - AAA Pattern - Arrange, Act, Assert
- Test behavior, not implementation
- Fast tests - Mock external dependencies
- Isolated tests - No shared state