Springboot Tdd

1---2name: springboot-tdd3description: Test-driven development for Spring Boot using JUnit 5, Mockito, MockMvc, Testcontainers, and JaCoCo. Use when adding features, fixing bugs, or refactoring.4origin: ECC5---6 7# Spring Boot TDD Workflow8 9TDD guidance for Spring Boot services with 80%+ coverage (unit + integration).10 11## When to Use12 13- New features or endpoints14- Bug fixes or refactors15- Adding data access logic or security rules16 17## Workflow18 191) Write tests first (they should fail)202) Implement minimal code to pass213) Refactor with tests green224) Enforce coverage (JaCoCo)23 24## Unit Tests (JUnit 5 + Mockito)25 26```java27@ExtendWith(MockitoExtension.class)28class MarketServiceTest {29  @Mock MarketRepository repo;30  @InjectMocks MarketService service;31 32  @Test33  void createsMarket() {34    CreateMarketRequest req = new CreateMarketRequest("name", "desc", Instant.now(), List.of("cat"));35    when(repo.save(any())).thenAnswer(inv -> inv.getArgument(0));36 37    Market result = service.create(req);38 39    assertThat(result.name()).isEqualTo("name");40    verify(repo).save(any());41  }42}43```44 45Patterns:46- Arrange-Act-Assert47- Avoid partial mocks; prefer explicit stubbing48- Use `@ParameterizedTest` for variants49 50## Web Layer Tests (MockMvc)51 52```java53@WebMvcTest(MarketController.class)54class MarketControllerTest {55  @Autowired MockMvc mockMvc;56  @MockBean MarketService marketService;57 58  @Test59  void returnsMarkets() throws Exception {60    when(marketService.list(any())).thenReturn(Page.empty());61 62    mockMvc.perform(get("/api/markets"))63        .andExpect(status().isOk())64        .andExpect(jsonPath("$.content").isArray());65  }66}67```68 69## Integration Tests (SpringBootTest)70 71```java72@SpringBootTest73@AutoConfigureMockMvc74@ActiveProfiles("test")75class MarketIntegrationTest {76  @Autowired MockMvc mockMvc;77 78  @Test79  void createsMarket() throws Exception {80    mockMvc.perform(post("/api/markets")81        .contentType(MediaType.APPLICATION_JSON)82        .content("""83          {"name":"Test","description":"Desc","endDate":"2030-01-01T00:00:00Z","categories":["general"]}84        """))85      .andExpect(status().isCreated());86  }87}88```89 90## Persistence Tests (DataJpaTest)91 92```java93@DataJpaTest94@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)95@Import(TestContainersConfig.class)96class MarketRepositoryTest {97  @Autowired MarketRepository repo;98 99  @Test100  void savesAndFinds() {101    MarketEntity entity = new MarketEntity();102    entity.setName("Test");103    repo.save(entity);104 105    Optional<MarketEntity> found = repo.findByName("Test");106    assertThat(found).isPresent();107  }108}109```110 111## Testcontainers112 113- Use reusable containers for Postgres/Redis to mirror production114- Wire via `@DynamicPropertySource` to inject JDBC URLs into Spring context115 116## Coverage (JaCoCo)117 118Maven snippet:119```xml120<plugin>121  <groupId>org.jacoco</groupId>122  <artifactId>jacoco-maven-plugin</artifactId>123  <version>0.8.14</version>124  <executions>125    <execution>126      <goals><goal>prepare-agent</goal></goals>127    </execution>128    <execution>129      <id>report</id>130      <phase>verify</phase>131      <goals><goal>report</goal></goals>132    </execution>133  </executions>134</plugin>135```136 137## Assertions138 139- Prefer AssertJ (`assertThat`) for readability140- For JSON responses, use `jsonPath`141- For exceptions: `assertThatThrownBy(...)`142 143## Test Data Builders144 145```java146class MarketBuilder {147  private String name = "Test";148  MarketBuilder withName(String name) { this.name = name; return this; }149  Market build() { return new Market(null, name, MarketStatus.ACTIVE); }150}151```152 153## CI Commands154 155- Maven: `mvn -T 4 test` or `mvn verify`156- Gradle: `./gradlew test jacocoTestReport`157 158**Remember**: Keep tests fast, isolated, and deterministic. Test behavior, not implementation details.