springboot-tdd

# 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()); } } ``` ## Integration Tests (SpringBootTest) ```java @SpringBootTest @AutoConfigureMockMvc @ActiveProfiles("test") class MarketIntegrationTest { @Autowired MockMvc mockMvc; @Test void createsMarket() throws Exception { mockMvc.perform(post("/api/markets") .contentType(MediaType.APPLICATION_JSON) .content(""" {"name":"Test","description":"Desc","endDate":"2030-01-01T00:00:00Z","categories":["general"]} """)) .andExpect(status().isCreated()); } } ``` ## Persistence Tests (DataJpaTest) ```java @DataJpaTest @AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE) @Import(TestContainersConfig.class) class MarketRepositoryTest { @Autowired MarketRepository repo; @Test void savesAndFinds() { MarketEntity entity = new MarketEntity(); entity.setName("Test"); repo.save(entity); Optional<MarketEntity> found = repo.findByName("Test"); assertThat(found).isPresent(); } } ``` ## Testcontainers - Use reusable containers for Postgres/Redis to mirror production - Wire via `@DynamicPropertySource` to inject JDBC URLs into Spring context ## Coverage (JaCoCo) Maven snippet: ```xml <plugin> <groupId>org.jacoco</groupId> <artifactId>jacoco-maven-plugin</artifactId> <version>0.8.14</version> <executions> <execution> <goals><goal>prepare-agent</goal></goals> </execution> <execution> <id>report</id> <phase>verify</phase> <goals><goal>report</goal></goals> </execution> </executions> </plugin> ``` ## Assertions - Prefer AssertJ (`assertThat`) for readability - For JSON responses, use `jsonPath` - For exceptions: `assertThatThrownBy(...)` ## Test Data Builders ```java class MarketBuilder { private String name = "Test"; MarketBuilder withName(String name) { this.name = name; return this; } Market build() { return new Market(null, name, MarketStatus.ACTIVE); } } ``` ## CI Commands - Maven: `mvn -T 4 test` or `mvn verify` - Gradle: `./gradlew test jacocoTestReport` **Remember**: Keep tests fast, isolated, and deterministic. Test behavior, not implementation details.