springboot-tdd

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Test-driven development for Spring Boot using JUnit 5, Mockito, MockMvc, Testcontainers, and JaCoCo. Use when adding features, fixing bugs, or refactoring.

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NPX Install

npx skill4agent add mark393295827/house-maint-ai springboot-tdd

SKILL.md Content

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.