Clean • Professional
Testing is a critical part of Spring Boot development. It ensures that your application behaves as expected, prevents regressions, and improves overall code quality. Spring Boot offers excellent built-in support for unit testing, integration testing, web layer testing, and end-to-end testing, built on top of JUnit 5, Mockito, and the Spring TestContext Framework.
Spring Boot Testing is the process of verifying that a Spring Boot application works correctly by testing its components such as controllers, services, repositories, and security using Spring Boot’s built-in testing support.
Spring Boot provides powerful testing tools and annotations that simplify writing unit tests, integration tests, web layer tests, and end-to-end tests with minimal configuration.
In Simple Terms :
Spring Boot Testing helps catch bugs early, ensures correct behavior, and prevents breaking changes as the application evolves.
Testing is not optional—it is a core part of building robust Spring Boot applications
Spring Boot supports multiple types of tests, and each type has a specific purpose. Using the right test type at the right place keeps your test suite fast, reliable, and maintainable.

Unit Testing focuses on testing a single class or component in isolation, without starting the Spring container or loading the application context.
Focus
Tools
@ExtendWith(MockitoExtension.class)@Mock, @InjectMocksExample
@ExtendWith(MockitoExtension.class)
class UserServiceTest {
@Mock
private UserRepository userRepository;
@InjectMocks
private UserService userService;
@Test
void testGetUserById() {
User user = new User(1L, "Alice");
Mockito.when(userRepository.findById(1L))
.thenReturn(Optional.of(user));
User result = userService.getUserById(1L);
Assertions.assertEquals("Alice", result.getName());
}
}
Unit tests verify logic, not framework behavior.
They should be fast, isolated, deterministic, and easy to maintain.
Integration Testing verifies how multiple components work together using the Spring application context.
Focus
Tools
@SpringBootTest@AutoConfigureMockMvc (for web integration)Example
@SpringBootTest
classUserServiceIntegrationTest {
@Autowired
private UserService userService;
@Test
voidtestUserCreation() {
Useruser=newUser(null,"Bob");
Usersaved= userService.createUser(user);
Assertions.assertNotNull(saved.getId());
}
}
Integration tests validate collaboration between components. They provide realistic confidence that your application works correctly as a whole.
Web Layer Testing focuses on testing REST controllers and HTTP endpoints only, without loading the full Spring application context.
Focus
Tools
@WebMvcTestMockMvc@MockBean (to mock dependencies)Example
@WebMvcTest(UserController.class)
class UserControllerTest {
@Autowired
private MockMvc mockMvc;
@MockBean
private UserService userService;
@Test
void testGetUserEndpoint() throws Exception {
Mockito.when(userService.getUserById(1L))
.thenReturn(new User(1L, "John Doe"));
mockMvc.perform(get("/api/users/1"))
.andExpect(status().isOk())
.andExpect(jsonPath("$.name").value("John Doe"));
}
}
Web layer tests validate API behavior without involving business logic or databases.
They are fast, focused, and essential for REST API reliability.
Repository Testing focuses on testing Spring Data JPA repositories, ensuring that database interactions work as expected.
Focus
Tools
@DataJpaTestTestEntityManager (optional, for fine-grained control)Example
@DataJpaTest
classUserRepositoryTest {
@Autowired
private UserRepository userRepository;
@Test
voidtestFindByUsername() {
Useruser=newUser(null,"Alice");
userRepository.save(user);
Userfound= userRepository.findByName("Alice");
Assertions.assertNotNull(found);
}
}
Repository tests validate database behavior, not business logic.
They provide confidence that your data layer is correctly mapped and queried.
End-to-End (E2E) Testing verifies the entire application flow, from incoming HTTP requests to database persistence and back to the response.
Focus
Tools
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)TestRestTemplate (Blocking)WebTestClient (Reactive / Modern)Example
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
classUserApiE2ETest {
@Autowired
private TestRestTemplate restTemplate;
@Test
voidtestUserCreationEndpoint() {
Useruser=newUser(null,"Charlie");
ResponseEntity<User> response =
restTemplate.postForEntity("/users", user, User.class);
Assertions.assertEquals(HttpStatus.OK, response.getStatusCode());
Assertions.assertEquals("Charlie", response.getBody().getName());
}
}
E2E tests provide the highest confidence but should be used sparingly due to execution cost.
Spring Boot applications often need specialized tests beyond the typical unit, integration, and E2E tests.
Many applications depend on third-party APIs (e.g., payment gateways, SMS/email services).
Testing against real services can be slow, unstable, or costly.
Approach:
@MockBean to mock Spring beans for external clientsBenefits:
Security testing ensures authentication and authorization rules work as intended.
Tools / Annotations:
@WithMockUser → Simulate authenticated users with roles@WithAnonymousUser → Test access for unauthenticated usersFocus:
Example:
@WebMvcTest(AdminController.class)
classAdminControllerTest {
@Autowired
private MockMvc mockMvc;
@Test
@WithMockUser(roles = "ADMIN")
voidadminAccessAllowed()throws Exception {
mockMvc.perform(get("/admin/dashboard"))
.andExpect(status().isOk());
}
@Test
@WithAnonymousUser
voidadminAccessDeniedForAnonymous()throws Exception {
mockMvc.perform(get("/admin/dashboard"))
.andExpect(status().isForbidden());
}
}
For applications using @Async, scheduled tasks, or CompletableFuture, testing must account for concurrency.
Approach:
@EnableAsyncCompletableFuture.get() or awaitility library to verify resultsFocus:
| Tool | Purpose |
|---|---|
| JUnit 5 | Core framework for unit and integration tests |
| Mockito | Mock dependencies for isolated testing |
| Spring Test / MockMvc | Test controllers and web layer without starting a server |
| Testcontainers | Spin up real databases or services in Docker containers for integration tests |
| AssertJ | Write fluent, readable, and expressive assertions |
| Test Type | Purpose | Annotation / Tool | Context Loaded |
|---|---|---|---|
| Unit | Test single component logic | Mockito, JUnit 5 | None (isolated) |
| Integration | Test multiple components together | @SpringBootTest, @AutoConfigureMockMvc | Full Spring context |
| Web / Controller | Test REST endpoints | @WebMvcTest, MockMvc | Web layer only |
| Repository / Data Layer | Test JPA & DB queries | @DataJpaTest, TestEntityManager | Partial (DB + repo) |
| E2E / Full Integration | End-to-end flow (API → DB) | @SpringBootTest(webEnvironment = RANDOM_PORT), TestRestTemplate | Full context, real infra |
| Security / External | Auth, role-based access, external services | @WithMockUser, @MockBean, WireMock | Partial / Full context |
Spring Boot Testing is essential for building robust, maintainable, and production-ready applications. By combining unit tests, integration tests, web layer tests, and end-to-end tests, developers can confidently deliver high-quality software while reducing bugs, enabling safe refactoring, and improving long-term reliability.