---
name: spring-boot-test-patterns
description: Provides comprehensive testing patterns for Spring Boot applications covering unit, integration, slice, and container-based testing with JUnit 5, Mockito, Testcontainers, and performance optimization. Use when writing tests, @Test methods, @MockBean mocks, or implementing test suites for Spring Boot applications.
allowed-tools: Read, Write, Edit, Bash, Glob, Grep
---
# Spring Boot Testing Patterns
## Overview
Comprehensive guidance for writing robust test suites for Spring Boot applications using JUnit 5, Mockito, Testcontainers, and performance-optimized slice testing patterns.
## When to Use
- Writing unit tests for services or repositories with mocked dependencies
- Implementing integration tests with real databases via Testcontainers
- Testing REST APIs with `@WebMvcTest` or MockMvc
- Configuring `@ServiceConnection` for container management in Spring Boot 3.5+
## Quick Reference
| Test Type | Annotation | Target Time | Use Case |
|-----------|------------|-------------|----------|
| **Unit Tests** | `@ExtendWith(MockitoExtension.class)` | < 50ms | Business logic without Spring context |
| **Repository Tests** | `@DataJpaTest` | < 100ms | Database operations with minimal context |
| **Controller Tests** | `@WebMvcTest` / `@WebFluxTest` | < 100ms | REST API layer testing |
| **Integration Tests** | `@SpringBootTest` | < 500ms | Full application context with containers |
| **Testcontainers** | `@ServiceConnection` / `@Testcontainers` | Varies | Real database/message broker containers |
## Core Concepts
### Test Architecture Philosophy
1. **Unit Tests** — Fast, isolated tests without Spring context (< 50ms)
2. **Slice Tests** — Minimal Spring context for specific layers (< 100ms)
3. **Integration Tests** — Full Spring context with real dependencies (< 500ms)
### Key Annotations
**Spring Boot Test:**
- `@SpringBootTest` — Full application context (use sparingly)
- `@DataJpaTest` — JPA components only (repositories, entities)
- `@WebMvcTest` — MVC layer only (controllers, `@ControllerAdvice`)
- `@WebFluxTest` — WebFlux layer only (reactive controllers)
- `@JsonTest` — JSON serialization components only
**Testcontainers:**
- `@ServiceConnection` — Wire Testcontainer to Spring Boot (3.5+)
- `@DynamicPropertySource` — Register dynamic properties at runtime
- `@Testcontainers` — Enable Testcontainers lifecycle management
## Instructions
### 1. Unit Testing Pattern
Test business logic with mocked dependencies:
```java
@ExtendWith(MockitoExtension.class)
class UserServiceTest {
@Mock
private UserRepository userRepository;
@InjectMocks
private UserService userService;
@Test
void shouldFindUserByIdWhenExists() {
when(userRepository.findById(1L)).thenReturn(Optional.of(user));
Optional<User> result = userService.findById(1L);
assertThat(result).isPresent();
verify(userRepository).findById(1L);
}
}
```
See [unit-testing.md](references/unit-testing.md) for advanced patterns.
### 2. Slice Testing Pattern
Use focused test slices for specific layers:
```java
@DataJpaTest
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
@TestContainerConfig
class UserRepositoryIntegrationTest {
@Autowired
private UserRepository userRepository;
@Test
void shouldSaveAndRetrieveUser() {
User saved = userRepository.save(user);
assertThat(userRepository.findByEmail("[email protected]")).isPresent();
}
}
```
See [slice-testing.md](references/slice-testing.md) for all slice patterns.
### 3. REST API Testing Pattern
Test controllers with MockMvc:
```java
@WebMvcTest(UserController.class)
class UserControllerTest {
@Autowired
private MockMvc mockMvc;
@MockBean
private UserService userService;
@Test
void shouldGetUserById() throws Exception {
mockMvc.perform(get("/api/users/1"))
.andExpect(status().isOk())
.andExpect(jsonPath("$.email").value("[email protected]"));
}
}
```
### 4. Testcontainers with `@ServiceConnection`
Configure containers with Spring Boot 3.5+:
```java
@TestConfiguration
public class TestContainerConfig {
@Bean
@ServiceConnection
public PostgreSQLContainer<?> postgresContainer() {
return new PostgreSQLContainer<>("postgres:16-alpine");
}
}
```
Apply with `@Import(TestContainerConfig.class)` on test classes.
See [testcontainers-setup.md](references/testcontainers-setup.md) for detailed configuration.
### 5. Add Dependencies
Include required testing dependencies:
```xml
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.testcontainers</groupId>
<artifactId>junit-jupiter</artifactId>
<version>1.19.0</version>
<scope>test</scope>
</dependency>
```
See [test-dependencies.md](references/test-dependencies.md) for complete dependency list.
### 6. Configure CI/CD
Set up GitHub Actions for automated testing:
```yaml
name: Tests
on: [push, pull_request]
jobs:
test:
runs-on: ubuntu-latest
services:
docker:
image: docker:20-dind
steps:
- uses: actions/checkout@v4
- name: Set up JDK 17
uses: actions/setup-java@v4
with:
distribution: 'temurin'
- name: Run tests
run: ./mvnw test
```
See [ci-cd-configuration.md](references/ci-cd-configuration.md) for full CI/CD patterns.
### Validation Checkpoints
After implementing tests, verify:
- Container running: `docker ps` (look for testcontainer images)
- Context loaded: check startup logs for "Started Application in X.XX seconds"
- Test isolation: run tests individually and confirm no cross-contamination
## Examples
### Full Integration Test with `@ServiceConnection`
```java
@SpringBootTest
@Import(TestContainerConfig.class)
class OrderServiceIntegrationTest {
@Autowired
private OrderService orderService;
@Autowired
private UserRepository userRepository;
@Test
void shouldCreateOrderForExistingUser() {
User user = userRepository.save(User.builder()
.email("[email protected]")
.build());
Order order = orderService.createOrder(user.getId(), List.of(
new OrderItem("SKU-001", 2)
));
assertThat(order.getId()).isNotNull();
assertThat(order.getStatus()).isEqualTo(OrderStatus.PENDING);
}
}
```
### `@DataJpaTest` with Real Database
```java
@DataJpaTest
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
@TestContainerConfig
class UserRepositoryTest {
@Autowired
private UserRepository userRepository;
@Test
void shouldFindByEmail() {
userRepository.save(User.builder()
.email("[email protected]")
.build());
assertThat(userRepository.findByEmail("[email protected]"))
.isPresent();
}
}
```
See [workflow-patterns.md](references/workflow-patterns.md) for complete end-to-end examples.
## Best Practices
- **Use the right test type**: `@DataJpaTest` for repositories, `@WebMvcTest` for controllers, `@SpringBootTest` only for full integration
- **Prefer `@ServiceConnection`** on Spring Boot 3.5+ for cleaner container management over `@DynamicPropertySource`
- **Keep tests deterministic**: Initialize all test data explicitly in `@BeforeEach`
- **Organize by layer**: Group tests by layer to maximize context caching
- **Reuse Testcontainers** at JVM level (`withReuse(true)` + `TESTCONTAINERS_REUSE_ENABLE=true`)
- **Avoid `@DirtiesContext`**: Forces context rebuild, significantly hurts performance
- **Mock external services**, use real databases only when necessary
- **Performance targets**: Unit < 50ms, Slice < 100ms, Integration < 500ms
## Constraints and Warnings
- Never use `@DirtiesContext` unless absolutely necessary (forces context rebuild)
- Avoid mixing `@MockBean` with different configurations (creates separate contexts)
- Testcontainers require Docker; ensure CI/CD pipelines have Docker support
- Do not rely on test execution order; each test must be independent
- Be cautious with `@TestPropertySource` (creates separate contexts)
- Do not use `@SpringBootTest` for unit tests; use plain Mockito instead
- Context caching can be invalidated by different `@MockBean` configurations
- Avoid static mutable state in tests (causes flaky tests)
## References
- **[test-dependencies.md](references/test-dependencies.md)** — Maven/Gradle test dependencies
- **[unit-testing.md](references/unit-testing.md)** — Unit testing with Mockito patterns
- **[slice-testing.md](references/slice-testing.md)** — Repository, controller, and JSON slice tests
- **[testcontainers-setup.md](references/testcontainers-setup.md)** — Testcontainers configuration patterns
- **[ci-cd-configuration.md](references/ci-cd-configuration.md)** — GitHub Actions, GitLab CI, Docker Compose
- **[api-reference.md](references/api-reference.md)** — Complete test annotations and utilities
- **[best-practices.md](references/best-practices.md)** — Testing patterns and optimization
- **[workflow-patterns.md](references/workflow-patterns.md)** — Complete integration test examples