Springboot Tdd

---
name: springboot-tdd
description: Test-driven development for Spring Boot using JUnit 5, Mockito, MockMvc, Testcontainers, and JaCoCo. Use when adding features, fixing bugs, or refactoring.
metadata:
  origin: ECC
---

# Spring Boot TDD Workflow

TDD guidance for Spring Boot services with 80%+ coverage (unit + integration).

## When to Use

- New features or endpoints
- Bug fixes or refactors
- Adding data access logic or security rules

## Workflow

1) Write tests first (they should fail)
2) Implement minimal code to pass
3) Refactor with tests green
4) Enforce coverage (JaCoCo)

## Unit Tests (JUnit 5 + Mockito)

```java
@ExtendWith(MockitoExtension.class)
class MarketServiceTest {
  @Mock MarketRepository repo;
  @InjectMocks MarketService service;

  @Test
  void createsMarket() {
    CreateMarketRequest req = new CreateMarketRequest("name", "desc", Instant.now(), List.of("cat"));
    when(repo.save(any())).thenAnswer(inv -> inv.getArgument(0));

    Market result = service.create(req);

    assertThat(result.name()).isEqualTo("name");
    verify(repo).save(any());
  }
}
```

Patterns:
- Arrange-Act-Assert
- Avoid partial mocks; prefer explicit stubbing
- Use `@ParameterizedTest` for variants

## Web Layer Tests (MockMvc)

```java
@WebMvcTest(MarketController.class)
class MarketControllerTest {
  @Autowired MockMvc mockMvc;
  @MockBean MarketService marketService;

  @Test
  void returnsMarkets() throws Exception {
    when(marketService.list(any())).thenReturn(Page.empty());

    mockMvc.perform(get("/api/markets"))
        .andExpect(status().isOk())
        .andExpect(jsonPath("$.content").isArray());