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 Write tests first (they should fail) Implement minimal code to pass Refactor with tests green Enforce coverage (JaCoCo) Unit Tests (JUnit 5 + Mockito) @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) @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) @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) @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: < 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 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.