tomevault-io Spring Boot Testing Patterns
Overview
This skill provides comprehensive guidance for writing robust test suites for Spring Boot applications. It covers unit testing with Mockito, integration testing with Testcontainers, performance-optimized slice testing patterns, and best practices for maintaining fast feedback loops.
When to Use This Skill
Use this skill when:
- Writing unit tests for services, repositories, or utilities
- Implementing integration tests with real databases using Testcontainers
- Setting up performance-optimized test slices (@DataJpaTest, @WebMvcTest)
- Configuring Spring Boot 3.5+ @ServiceConnection for container management
- Testing REST APIs with MockMvc, TestRestTemplate, or WebTestClient
- Optimizing test performance through context caching and container reuse
- Setting up CI/CD pipelines for integration tests
- Implementing comprehensive test strategies for monolithic or microservices applications
Core Concepts
Test Architecture Philosophy
Spring Boot testing follows a layered approach with distinct test types:
1. Unit Tests
- Fast, isolated tests without Spring context
- Use Mockito for dependency injection
- Focus on business logic validation
- Target completion time: < 50ms per test
2. Slice Tests
- Minimal Spring context loading for specific layers
- Use @DataJpaTest for repository tests
- Use @WebMvcTest for controller tests
- Use @WebFluxTest for reactive controller tests
- Target completion time: < 100ms per test
3. Integration Tests
- Full Spring context with real dependencies
- Use @SpringBootTest with @ServiceConnection containers
- Test complete application flows
- Target completion time: < 500ms per test
Key Testing Annotations
Spring Boot Test Annotations:
@SpringBootTest: Load full application context (use sparingly)@DataJpaTest: Load only JPA components (repositories, entities)@WebMvcTest: Load only MVC layer (controllers, @ControllerAdvice)@WebFluxTest: Load only WebFlux layer (reactive controllers)@JsonTest: Load only JSON serialization components
Testcontainer Annotations:
@ServiceConnection: Wire Testcontainer to Spring Boot test (Spring Boot 3.5+)@DynamicPropertySource: Register dynamic properties at runtime@Testcontainers: Enable Testcontainers lifecycle management
Dependencies
Maven Dependencies
<dependencies>
<!-- Spring Boot Test Starter -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- Testcontainers -->
<dependency>
<groupId>org.testcontainers</groupId>
<artifactId>junit-jupiter</artifactId>
<version>1.19.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.testcontainers</groupId>
<artifactId>postgresql</artifactId>
<version>1.19.0</version>
<scope>test</scope>
</dependency>
<!-- Additional Testing Dependencies -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
Gradle Dependencies
dependencies {
// Spring Boot Test Starter
testImplementation("org.springframework.boot:spring-boot-starter-test")
// Testcontainers
testImplementation("org.testcontainers:junit-jupiter:1.19.0")
testImplementation("org.testcontainers:postgresql:1.19.0")
// Additional Dependencies
implementation("org.springframework.boot:spring-boot-starter-data-jpa")
implementation("org.springframework.boot:spring-boot-starter-web")
}
Instructions
Unit Testing Pattern
Test business logic with mocked dependencies:
class UserServiceTest {
@Mock
private UserRepository userRepository;
@InjectMocks
private UserService userService;
@BeforeEach
void setUp() {
MockitoAnnotations.openMocks(this);
}
@Test
void shouldFindUserByIdWhenExists() {
// Arrange
Long userId = 1L;
User user = new User();
user.setId(userId);
user.setEmail("test@example.com");
when(userRepository.findById(userId)).thenReturn(Optional.of(user));
// Act
Optional<User> result = userService.findById(userId);
// Assert
assertThat(result).isPresent();
assertThat(result.get().getEmail()).isEqualTo("test@example.com");
verify(userRepository, times(1)).findById(userId);
}
}
Slice Testing Pattern
Use focused test slices for specific layers:
// Repository test with minimal context
@DataJpaTest
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
@TestContainerConfig
public class UserRepositoryIntegrationTest {
@Autowired
private UserRepository userRepository;
@Test
void shouldSaveAndRetrieveUserFromDatabase() {
// Arrange
User user = new User();
user.setEmail("test@example.com");
user.setName("Test User");
// Act
User saved = userRepository.save(user);
userRepository.flush();
Optional<User> retrieved = userRepository.findByEmail("test@example.com");
// Assert
assertThat(retrieved).isPresent();
assertThat(retrieved.get().getName()).isEqualTo("Test User");
}
}
REST API Testing Pattern
Test controllers with MockMvc for faster execution:
@SpringBootTest
@AutoConfigureMockMvc
@Transactional
public class UserControllerIntegrationTest {
@Autowired
private MockMvc mockMvc;
@Autowired
private ObjectMapper objectMapper;
@Autowired
private UserService userService;
@Test
void shouldCreateUserAndReturn201() throws Exception {
User user = new User();
user.setEmail("newuser@example.com");
user.setName("New User");
mockMvc.perform(post("/api/users")
.contentType(MediaType.APPLICATION_JSON)
.content(objectMapper.writeValueAsString(user)))
.andExpect(status().isCreated())
.andExpect(jsonPath("$.id").exists())
.andExpect(jsonPath("$.email").value("newuser@example.com"))
.andExpect(jsonPath("$.name").value("New User"));
}
}
Testcontainers with @ServiceConnection
Configure containers with Spring Boot 3.5+:
@TestConfiguration
public class TestContainerConfig {
@Bean
@ServiceConnection
public PostgreSQLContainer<?> postgresContainer() {
return new PostgreSQLContainer<>(DockerImageName.parse("postgres:16-alpine"))
.withDatabaseName("testdb")
.withUsername("test")
.withPassword("test");
}
}
Examples
Basic Unit Test
@Test
void shouldCalculateTotalPrice() {
// Arrange
OrderItem item1 = new OrderItem();
item1.setPrice(10.0);
item1.setQuantity(2);
OrderItem item2 = new OrderItem();
item2.setPrice(15.0);
item2.setQuantity(1);
List<OrderItem> items = List.of(item1, item2);
// Act
double total = orderService.calculateTotal(items);
// Assert
assertThat(total).isEqualTo(35.0);
}
Integration Test with Testcontainers
@SpringBootTest
@TestContainerConfig
public class OrderServiceIntegrationTest {
@Autowired
private OrderService orderService;
@Autowired
private UserRepository userRepository;
@MockBean
private PaymentService paymentService;
@Test
void shouldCreateOrderWithRealDatabase() {
// Arrange
User user = new User();
user.setEmail("customer@example.com");
user.setName("John Doe");
User savedUser = userRepository.save(user);
OrderRequest request = new OrderRequest();
request.setUserId(savedUser.getId());
request.setItems(List.of(
new OrderItemRequest(1L, 2),
new OrderItemRequest(2L, 1)
));
when(paymentService.processPayment(any())).thenReturn(true);
// Act
OrderResponse response = orderService.createOrder(request);
// Assert
assertThat(response.getOrderId()).isNotNull();
assertThat(response.getStatus()).isEqualTo("COMPLETED");
verify(paymentService, times(1)).processPayment(any());
}
}
Reactive Test Pattern
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@AutoConfigureWebTestClient
public class ReactiveUserControllerIntegrationTest {
@Autowired
private WebTestClient webTestClient;
@Test
void shouldReturnUserAsJsonReactive() {
// Arrange
User user = new User();
user.setEmail("reactive@example.com");
user.setName("Reactive User");
// Act & Assert
webTestClient.get()
.uri("/api/users/1")
.exchange()
.expectStatus().isOk()
.expectBody()
.jsonPath("$.email").isEqualTo("reactive@example.com")
.jsonPath("$.name").isEqualTo("Reactive User");
}
}
Best Practices
1. Choose the Right Test Type
Select appropriate test annotations based on scope:
// Use @DataJpaTest for repository-only tests (fastest)
@DataJpaTest
public class UserRepositoryTest { }
// Use @WebMvcTest for controller-only tests
@WebMvcTest(UserController.class)
public class UserControllerTest { }
// Use @SpringBootTest only for full integration testing
@SpringBootTest
public class UserServiceFullIntegrationTest { }
2. Use @ServiceConnection for Container Management
Prefer @ServiceConnection over manual @DynamicPropertySource for cleaner code:
// Good - Spring Boot 3.5+
@TestConfiguration
public class TestConfig {
@Bean
@ServiceConnection
public PostgreSQLContainer<?> postgres() {
return new PostgreSQLContainer<>(DockerImageName.parse("postgres:16-alpine"));
}
}
3. Keep Tests Deterministic
Always initialize test data explicitly:
// Good - Explicit setup
@BeforeEach
void setUp() {
userRepository.deleteAll();
User user = new User();
user.setEmail("test@example.com");
userRepository.save(user);
}
// Avoid - Depending on other tests
@Test
void testUserExists() {
// Assumes previous test created a user
Optional<User> user = userRepository.findByEmail("test@example.com");
assertThat(user).isPresent();
}
4. Use Meaningful Assertions
Leverage AssertJ for readable, fluent assertions:
// Good - Clear, readable assertions
assertThat(user.getEmail())
.isEqualTo("test@example.com");
assertThat(users)
.hasSize(3)
.contains(expectedUser);
// Avoid - JUnit assertions
assertEquals("test@example.com", user.getEmail());
assertTrue(users.size() == 3);
5. Organize Tests by Layer
Group related tests in separate classes to optimize context caching:
// Repository tests (uses @DataJpaTest)
public class UserRepositoryTest { }
// Controller tests (uses @WebMvcTest)
public class UserControllerTest { }
// Service tests (uses mocks, no context)
public class UserServiceTest { }
// Full integration tests (uses @SpringBootTest)
public class UserFullIntegrationTest { }
Performance Optimization
Context Caching Strategy
Maximize Spring context caching by grouping tests with similar configurations:
// Group repository tests with same configuration
@DataJpaTest
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
@TestContainerConfig
@TestPropertySource(properties = "spring.datasource.url=jdbc:postgresql:testdb")
public class UserRepositoryTest { }
// Group controller tests with same configuration
@WebMvcTest(UserController.class)
@AutoConfigureMockMvc
public class UserControllerTest { }
Container Reuse Strategy
Reuse Testcontainers at JVM level for better performance:
@Testcontainers
public class ContainerConfig {
static final PostgreSQLContainer<?> POSTGRES = new PostgreSQLContainer<>(
DockerImageName.parse("postgres:16-alpine"))
.withDatabaseName("testdb")
.withUsername("test")
.withPassword("test");
@BeforeAll
static void startAll() {
POSTGRES.start();
}
@AfterAll
static void stopAll() {
POSTGRES.stop();
}
}
Test Execution
Maven Test Execution
# Run all tests
./mvnw test
# Run specific test class
./mvnw test -Dtest=UserServiceTest
# Run integration tests only
./mvnw test -Dintegration-test=true
# Run tests with coverage
./mvnw clean jacoco:prepare-agent test jacoco:report
Gradle Test Execution
# Run all tests
./gradlew test
# Run specific test class
./gradlew test --tests UserServiceTest
# Run integration tests only
./gradlew integrationTest
# Run tests with coverage
./gradlew test jacocoTestReport
CI/CD Configuration
GitHub Actions Example
name: Spring Boot Tests
on: [push, pull_request]
jobs:
test:
runs-on: ubuntu-latest
services:
postgres:
image: postgres:16-alpine
env:
POSTGRES_PASSWORD: test
POSTGRES_USER: test
POSTGRES_DB: testdb
options: >-
--health-cmd pg_isready
--health-interval 10s
--health-timeout 5s
--health-retries 5
steps:
- uses: actions/checkout@v3
- name: Set up JDK 17
uses: actions/setup-java@v3
with:
java-version: '17'
distribution: 'temurin'
- name: Cache Maven dependencies
uses: actions/cache@v3
with:
path: ~/.m2/repository
key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
restore-keys: ${{ runner.os }}-maven-
- name: Run tests
run: ./mvnw test -Dspring.profiles.active=test
Docker Compose for Local Testing
version: '3.8'
services:
postgres:
image: postgres:16-alpine
environment:
POSTGRES_DB: testdb
POSTGRES_USER: test
POSTGRES_PASSWORD: test
ports:
- "5432:5432"
volumes:
- postgres_data:/var/lib/postgresql/data
volumes:
postgres_data:
References
For detailed information, refer to the following resources:
- API Reference - Complete test annotations and utilities
- Best Practices - Testing patterns and optimization
- Workflow Patterns - Complete integration test examples
Related Skills
- spring-boot-dependency-injection - Unit testing patterns with constructor injection
- spring-boot-rest-api-standards - REST API patterns to test
- spring-boot-crud-patterns - CRUD patterns to test
- unit-test-service-layer - Advanced service layer testing techniques
Performance Targets
- Unit tests: < 50ms per test
- Slice tests: < 100ms per test
- Integration tests: < 500ms per test
- Maximize context caching by grouping tests with same configuration
- Reuse Testcontainers at JVM level where possible
Key Principles
- Use test slices for focused, fast tests
- Prefer @ServiceConnection on Spring Boot 3.5+
- Keep tests deterministic with explicit setup
- Mock external dependencies, use real databases
- Avoid @DirtiesContext unless absolutely necessary
- Organize tests by layer to optimize context reuse
This skill enables building comprehensive test suites that validate Spring Boot applications reliably while maintaining fast feedback loops for development.
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