Imported from majiayu000/claude-skill-registry (skills/data/spring-tdd-mockito/SKILL.md). Install upstream with npx skills add majiayu000/claude-skill-registry --skill spring-tdd-mockito. Copyright stays with the author.

Spring Boot TDD with Mockito

TDD Cycle: Red → Green → Refactor

┌─────────────────────────────────────────────────────────────┐
│                     TDD WORKFLOW                             │
│                                                              │
│   ┌───────┐      ┌───────┐      ┌──────────┐               │
│   │  RED  │ ───→ │ GREEN │ ───→ │ REFACTOR │ ───┐          │
│   │       │      │       │      │          │    │          │
│   │ Write │      │ Write │      │ Improve  │    │          │
│   │ Test  │      │ Code  │      │ Code     │    │          │
│   └───────┘      └───────┘      └──────────┘    │          │
│       ↑                                          │          │
│       └──────────────────────────────────────────┘          │
└─────────────────────────────────────────────────────────────┘

Mockito Annotations

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

1. One assertion per test - Focus on single behavior
2. Descriptive test names - Use @DisplayName
3. AAA Pattern - Arrange, Act, Assert
4. Test behavior, not implementation
5. Fast tests - Mock external dependencies
6. Isolated tests - No shared state