43. Testing

Spring Boot provides a number of utilities and annotations to help when testing your application. Test support is provided by two modules: spring-boot-test contains core items, and spring-boot-test-autoconfigure supports auto-configuration for tests.

Most developers use the spring-boot-starter-test “Starter”, which imports both Spring Boot test modules as well as JUnit, AssertJ, Hamcrest, and a number of other useful libraries.

43.1 Test Scope Dependencies

The spring-boot-starter-test “Starter” (in the test scope) contains the following provided libraries:

  • JUnit: The de-facto standard for unit testing Java applications.
  • Spring Test & Spring Boot Test: Utilities and integration test support for Spring Boot applications.
  • AssertJ: A fluent assertion library.
  • Hamcrest: A library of matcher objects (also known as constraints or predicates).
  • Mockito: A Java mocking framework.
  • JSONassert: An assertion library for JSON.
  • JsonPath: XPath for JSON.

We generally find these common libraries to be useful when writing tests. If these libraries do not suit your needs, you can add additional test dependencies of your own.

43.2 Testing Spring Applications

One of the major advantages of dependency injection is that it should make your code easier to unit test. You can instantiate objects by using the new operator without even involving Spring. You can also use mock objects instead of real dependencies.

Often, you need to move beyond unit testing and start integration testing (with a Spring ApplicationContext). It is useful to be able to perform integration testing without requiring deployment of your application or needing to connect to other infrastructure.

The Spring Framework includes a dedicated test module for such integration testing. You can declare a dependency directly to org.springframework:spring-test or use the spring-boot-starter-test “Starter” to pull it in transitively.

If you have not used the spring-test module before, you should start by reading the relevant section of the Spring Framework reference documentation.

43.3 Testing Spring Boot Applications

A Spring Boot application is a Spring ApplicationContext, so nothing very special has to be done to test it beyond what you would normally do with a vanilla Spring context.

[Note]Note

External properties, logging, and other features of Spring Boot are installed in the context by default only if you use SpringApplication to create it.

Spring Boot provides a @SpringBootTest annotation, which can be used as an alternative to the standard spring-test @ContextConfiguration annotation when you need Spring Boot features. The annotation works by creating the ApplicationContext used in your tests through SpringApplication. In addition to @SpringBootTest a number of other annotations are also provided for testing more specific slices of an application.

[Tip]Tip

Don’t forget to also add @RunWith(SpringRunner.class) to your test, otherwise the annotations will be ignored.

By default, @SpringBootTest will not start a server. You can use the webEnvironment attribute of @SpringBootTest to further refine how your tests run:

  • MOCK(Default) : Loads a web ApplicationContext and provides a mock web environment. Embedded servers are not started when using this annotation. If a web environment is not available on your classpath, this mode transparently falls back to creating a regular non-web ApplicationContext. It can be used in conjunction with @AutoConfigureMockMvc or @AutoConfigureWebTestClient for mock-based testing of your web application.
  • RANDOM_PORT: Loads a WebServerApplicationContext and provides a real web environment. Embedded servers are started and listen on a random port.
  • DEFINED_PORT: Loads a WebServerApplicationContext and provides a real web environment. Embedded servers are started and listen on a defined port (from your application.properties or on the default port of 8080).
  • NONE: Loads an ApplicationContext by using SpringApplication but does not provide any web environment (mock or otherwise).
[Note]Note

If your test is @Transactional, it rolls back the transaction at the end of each test method by default. However, as using this arrangement with either RANDOM_PORT or DEFINED_PORT implicitly provides a real servlet environment, the HTTP client and server run in separate threads and, thus, in separate transactions. Any transaction initiated on the server does not roll back in this case.

43.3.1 Detecting Web Application Type

If Spring MVC is available, a regular MVC-based application context is configured. If you have only Spring WebFlux, we’ll detect that and configure a WebFlux-based application context instead.

If both are present, Spring MVC takes precedence. If you want to test a reactive web application in this scenario, you must set the spring.main.web-application-type property:

@RunWith(SpringRunner.class)
@SpringBootTest(properties = "spring.main.web-application-type=reactive")
public class MyWebFluxTests { ... }

43.3.2 Detecting Test Configuration

If you are familiar with the Spring Test Framework, you may be used to using @ContextConfiguration(classes=…​) in order to specify which Spring @Configuration to load. Alternatively, you might have often used nested @Configuration classes within your test.

When testing Spring Boot applications, this is often not required. Spring Boot’s @*Test annotations search for your primary configuration automatically whenever you do not explicitly define one.

The search algorithm works up from the package that contains the test until it finds a class annotated with @SpringBootApplication or @SpringBootConfiguration. As long as you structured your code in a sensible way, your main configuration is usually found.

[Note]Note

If you use a test annotation to test a more specific slice of your application, you should avoid adding configuration settings that are specific to a particular area on the main method’s application class.

The underlying component scan configuration of @SpringBootApplication defines exclude filters that are used to make sure slicing works as expected. If you are using an explicit @ComponentScan directive on your @SpringBootApplication-annotated class, be aware that those filters will be disabled. If you are using slicing, you should define them again.

If you want to customize the primary configuration, you can use a nested @TestConfiguration class. Unlike a nested @Configuration class, which would be used instead of your application’s primary configuration, a nested @TestConfiguration class is used in addition to your application’s primary configuration.

[Note]Note

Spring’s test framework caches application contexts between tests. Therefore, as long as your tests share the same configuration (no matter how it is discovered), the potentially time-consuming process of loading the context happens only once.

43.3.3 Excluding Test Configuration

If your application uses component scanning (for example, if you use @SpringBootApplication or @ComponentScan), you may find top-level configuration classes that you created only for specific tests accidentally get picked up everywhere.

As we have seen earlier, @TestConfiguration can be used on an inner class of a test to customize the primary configuration. When placed on a top-level class, @TestConfiguration indicates that classes in src/test/java should not be picked up by scanning. You can then import that class explicitly where it is required, as shown in the following example:

@RunWith(SpringRunner.class)
@SpringBootTest
@Import(MyTestsConfiguration.class)
public class MyTests {

	@Test
	public void exampleTest() {
		...
	}

}
[Note]Note

If you directly use @ComponentScan (that is, not through @SpringBootApplication) you need to register the TypeExcludeFilter with it. See the Javadoc for details.

43.3.4 Testing with a mock environment

By default, @SpringBootTest does not start the server. If you have web endpoints that you want to test against this mock environment, you can additionally configure MockMvc as shown in the following example:

import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;

import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
public class MockMvcExampleTests {

	@Autowired
	private MockMvc mvc;

	@Test
	public void exampleTest() throws Exception {
		this.mvc.perform(get("/")).andExpect(status().isOk())
				.andExpect(content().string("Hello World"));
	}

}
[Tip]Tip

If you want to focus only on the web layer and not start a complete ApplicationContext, consider using @WebMvcTest instead.

Alternatively, you can configure a WebTestClient as shown in the following example:

import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.AutoConfigureWebTestClient;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.reactive.server.WebTestClient;

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureWebTestClient
public class MockWebTestClientExampleTests {

	@Autowired
	private WebTestClient webClient;

	@Test
	public void exampleTest() {
		this.webClient.get().uri("/").exchange().expectStatus().isOk()
				.expectBody(String.class).isEqualTo("Hello World");
	}

}

43.3.5 Testing with a running server

If you need to start a full running server, we recommend that you use random ports. If you use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT), an available port is picked at random each time your test runs.

The @LocalServerPort annotation can be used to inject the actual port used into your test. For convenience, tests that need to make REST calls to the started server can additionally @Autowire a WebTestClient, which resolves relative links to the running server and comes with a dedicated API for verifying responses, as shown in the following example:

import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.reactive.server.WebTestClient;

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
public class RandomPortWebTestClientExampleTests {

	@Autowired
	private WebTestClient webClient;

	@Test
	public void exampleTest() {
		this.webClient.get().uri("/").exchange().expectStatus().isOk()
				.expectBody(String.class).isEqualTo("Hello World");
	}

}

This setup requires spring-webflux on the classpath. If you can’t or won’t add webflux, Spring Boot also provides a TestRestTemplate facility:

import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.test.context.junit4.SpringRunner;

import static org.assertj.core.api.Assertions.assertThat;

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
public class RandomPortTestRestTemplateExampleTests {

	@Autowired
	private TestRestTemplate restTemplate;

	@Test
	public void exampleTest() {
		String body = this.restTemplate.getForObject("/", String.class);
		assertThat(body).isEqualTo("Hello World");
	}

}

43.3.6 Using JMX

As the test context framework caches context, JMX is disabled by default to prevent identical components to register on the same domain. If such test needs access to an MBeanServer, consider marking it dirty as well:

@RunWith(SpringRunner.class)
@SpringBootTest(properties = "spring.jmx.enabled=true")
@DirtiesContext
public class SampleJmxTests {

	@Autowired
	private MBeanServer mBeanServer;

	@Test
	public void exampleTest() {
		// ...
	}

}

43.3.7 Mocking and Spying Beans

When running tests, it is sometimes necessary to mock certain components within your application context. For example, you may have a facade over some remote service that is unavailable during development. Mocking can also be useful when you want to simulate failures that might be hard to trigger in a real environment.

Spring Boot includes a @MockBean annotation that can be used to define a Mockito mock for a bean inside your ApplicationContext. You can use the annotation to add new beans or replace a single existing bean definition. The annotation can be used directly on test classes, on fields within your test, or on @Configuration classes and fields. When used on a field, the instance of the created mock is also injected. Mock beans are automatically reset after each test method.

[Note]Note

If your test uses one of Spring Boot’s test annotations (such as @SpringBootTest), this feature is automatically enabled. To use this feature with a different arrangement, a listener must be explicitly added, as shown in the following example:

@TestExecutionListeners(MockitoTestExecutionListener.class)

The following example replaces an existing RemoteService bean with a mock implementation:

import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.mock.mockito.*;
import org.springframework.test.context.junit4.*;

import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;

@RunWith(SpringRunner.class)
@SpringBootTest
public class MyTests {

	@MockBean
	private RemoteService remoteService;

	@Autowired
	private Reverser reverser;

	@Test
	public void exampleTest() {
		// RemoteService has been injected into the reverser bean
		given(this.remoteService.someCall()).willReturn("mock");
		String reverse = reverser.reverseSomeCall();
		assertThat(reverse).isEqualTo("kcom");
	}

}

Additionally, you can use @SpyBean to wrap any existing bean with a Mockito spy. See the Javadoc for full details.

[Note]Note

While Spring’s test framework caches application contexts between tests and reuses a context for tests sharing the same configuration, the use of @MockBean or @SpyBean influences the cache key, which will most likely increase the number of contexts.

43.3.8 Auto-configured Tests

Spring Boot’s auto-configuration system works well for applications but can sometimes be a little too much for tests. It often helps to load only the parts of the configuration that are required to test a “slice” of your application. For example, you might want to test that Spring MVC controllers are mapping URLs correctly, and you do not want to involve database calls in those tests, or you might want to test JPA entities, and you are not interested in the web layer when those tests run.

The spring-boot-test-autoconfigure module includes a number of annotations that can be used to automatically configure such “slices”. Each of them works in a similar way, providing a @…​Test annotation that loads the ApplicationContext and one or more @AutoConfigure…​ annotations that can be used to customize auto-configuration settings.

[Note]Note

Each slice restricts component scan to appropriate components and loads a very restricted set of auto-configuration classes. If you need to exclude one of them, most @…​Test annotations provide an excludeAutoConfiguration attribute. Alternatively, you can use @ImportAutoConfiguration#exclude.

[Tip]Tip

It is also possible to use the @AutoConfigure…​ annotations with the standard @SpringBootTest annotation. You can use this combination if you are not interested in “slicing” your application but you want some of the auto-configured test beans.

43.3.9 Auto-configured JSON Tests

To test that object JSON serialization and deserialization is working as expected, you can use the @JsonTest annotation. @JsonTest auto-configures the available supported JSON mapper, which can be one of the following libraries:

  • Jackson ObjectMapper, any @JsonComponent beans and any Jackson Modules
  • Gson
  • Jsonb
[Tip]Tip

A list of the auto-configurations that are enabled by @JsonTest can be found in the appendix.

If you need to configure elements of the auto-configuration, you can use the @AutoConfigureJsonTesters annotation.

Spring Boot includes AssertJ-based helpers that work with the JSONAssert and JsonPath libraries to check that JSON appears as expected. The JacksonTester, GsonTester, JsonbTester, and BasicJsonTester classes can be used for Jackson, Gson, Jsonb, and Strings respectively. Any helper fields on the test class can be @Autowired when using @JsonTest. The following example shows a test class for Jackson:

import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.json.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.json.*;
import org.springframework.test.context.junit4.*;

import static org.assertj.core.api.Assertions.*;

@RunWith(SpringRunner.class)
@JsonTest
public class MyJsonTests {

	@Autowired
	private JacksonTester<VehicleDetails> json;

	@Test
	public void testSerialize() throws Exception {
		VehicleDetails details = new VehicleDetails("Honda", "Civic");
		// Assert against a `.json` file in the same package as the test
		assertThat(this.json.write(details)).isEqualToJson("expected.json");
		// Or use JSON path based assertions
		assertThat(this.json.write(details)).hasJsonPathStringValue("@.make");
		assertThat(this.json.write(details)).extractingJsonPathStringValue("@.make")
				.isEqualTo("Honda");
	}

	@Test
	public void testDeserialize() throws Exception {
		String content = "{\"make\":\"Ford\",\"model\":\"Focus\"}";
		assertThat(this.json.parse(content))
				.isEqualTo(new VehicleDetails("Ford", "Focus"));
		assertThat(this.json.parseObject(content).getMake()).isEqualTo("Ford");
	}

}
[Note]Note

JSON helper classes can also be used directly in standard unit tests. To do so, call the initFields method of the helper in your @Before method if you do not use @JsonTest.

43.3.10 Auto-configured Spring MVC Tests

To test whether Spring MVC controllers are working as expected, use the @WebMvcTest annotation. @WebMvcTest auto-configures the Spring MVC infrastructure and limits scanned beans to @Controller, @ControllerAdvice, @JsonComponent, Converter, GenericConverter, Filter, WebMvcConfigurer, and HandlerMethodArgumentResolver. Regular @Component beans are not scanned when using this annotation.

[Tip]Tip

A list of the auto-configuration settings that are enabled by @WebMvcTest can be found in the appendix.

[Tip]Tip

If you need to register extra components, such as the Jackson Module, you can import additional configuration classes by using @Import on your test.

Often, @WebMvcTest is limited to a single controller and is used in combination with @MockBean to provide mock implementations for required collaborators.

@WebMvcTest also auto-configures MockMvc. Mock MVC offers a powerful way to quickly test MVC controllers without needing to start a full HTTP server.

[Tip]Tip

You can also auto-configure MockMvc in a non-@WebMvcTest (such as @SpringBootTest) by annotating it with @AutoConfigureMockMvc. The following example uses MockMvc:

import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;

import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;

@RunWith(SpringRunner.class)
@WebMvcTest(UserVehicleController.class)
public class MyControllerTests {

	@Autowired
	private MockMvc mvc;

	@MockBean
	private UserVehicleService userVehicleService;

	@Test
	public void testExample() throws Exception {
		given(this.userVehicleService.getVehicleDetails("sboot"))
				.willReturn(new VehicleDetails("Honda", "Civic"));
		this.mvc.perform(get("/sboot/vehicle").accept(MediaType.TEXT_PLAIN))
				.andExpect(status().isOk()).andExpect(content().string("Honda Civic"));
	}

}
[Tip]Tip

If you need to configure elements of the auto-configuration (for example, when servlet filters should be applied) you can use attributes in the @AutoConfigureMockMvc annotation.

If you use HtmlUnit or Selenium, auto-configuration also provides an HTMLUnit WebClient bean and/or a WebDriver bean. The following example uses HtmlUnit:

import com.gargoylesoftware.phpunit.*;
import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;

import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;

@RunWith(SpringRunner.class)
@WebMvcTest(UserVehicleController.class)
public class MyHtmlUnitTests {

	@Autowired
	private WebClient webClient;

	@MockBean
	private UserVehicleService userVehicleService;

	@Test
	public void testExample() throws Exception {
		given(this.userVehicleService.getVehicleDetails("sboot"))
				.willReturn(new VehicleDetails("Honda", "Civic"));
		HtmlPage page = this.webClient.getPage("/sboot/vehicle.php");
		assertThat(page.getBody().getTextContent()).isEqualTo("Honda Civic");
	}

}
[Note]Note

By default, Spring Boot puts WebDriver beans in a special “scope” to ensure that the driver exits after each test and that a new instance is injected. If you do not want this behavior, you can add @Scope("singleton") to your WebDriver @Bean definition.

[Tip]Tip

Sometimes writing Spring MVC tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server.

43.3.11 Auto-configured Spring WebFlux Tests

To test that Spring WebFlux controllers are working as expected, you can use the @WebFluxTest annotation. @WebFluxTest auto-configures the Spring WebFlux infrastructure and limits scanned beans to @Controller, @ControllerAdvice, @JsonComponent, Converter, GenericConverter, and WebFluxConfigurer. Regular @Component beans are not scanned when the @WebFluxTest annotation is used.

[Tip]Tip

A list of the auto-configurations that are enabled by @WebFluxTest can be found in the appendix.

[Tip]Tip

If you need to register extra components, such as Jackson Module, you can import additional configuration classes using @Import on your test.

Often, @WebFluxTest is limited to a single controller and used in combination with the @MockBean annotation to provide mock implementations for required collaborators.

@WebFluxTest also auto-configures WebTestClient, which offers a powerful way to quickly test WebFlux controllers without needing to start a full HTTP server.

[Tip]Tip

You can also auto-configure WebTestClient in a non-@WebFluxTest (such as @SpringBootTest) by annotating it with @AutoConfigureWebTestClient. The following example shows a class that uses both @WebFluxTest and a WebTestClient:

import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.reactive.server.WebTestClient;

@RunWith(SpringRunner.class)
@WebFluxTest(UserVehicleController.class)
public class MyControllerTests {

	@Autowired
	private WebTestClient webClient;

	@MockBean
	private UserVehicleService userVehicleService;

	@Test
	public void testExample() throws Exception {
		given(this.userVehicleService.getVehicleDetails("sboot"))
				.willReturn(new VehicleDetails("Honda", "Civic"));
		this.webClient.get().uri("/sboot/vehicle").accept(MediaType.TEXT_PLAIN)
				.exchange()
				.expectStatus().isOk()
				.expectBody(String.class).isEqualTo("Honda Civic");
	}

}
[Tip]Tip

This setup is only supported by WebFlux applications as using WebTestClient in a mocked web application only works with WebFlux at the moment.

[Note]Note

@WebFluxTest cannot detect routes registered via the functional web framework. For testing RouterFunction beans in the context, consider importing your RouterFunction yourself via @Import or using @SpringBootTest.

[Tip]Tip

Sometimes writing Spring WebFlux tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server.

43.3.12 Auto-configured Data JPA Tests

You can use the @DataJpaTest annotation to test JPA applications. By default, it configures an in-memory embedded database, scans for @Entity classes, and configures Spring Data JPA repositories. Regular @Component beans are not loaded into the ApplicationContext.

[Tip]Tip

A list of the auto-configuration settings that are enabled by @DataJpaTest can be found in the appendix.

By default, data JPA tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@RunWith(SpringRunner.class)
@DataJpaTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
public class ExampleNonTransactionalTests {

}

Data JPA tests may also inject a TestEntityManager bean, which provides an alternative to the standard JPA EntityManager that is specifically designed for tests. If you want to use TestEntityManager outside of @DataJpaTest instances, you can also use the @AutoConfigureTestEntityManager annotation. A JdbcTemplate is also available if you need that. The following example shows the @DataJpaTest annotation in use:

import org.junit.*;
import org.junit.runner.*;
import org.springframework.boot.test.autoconfigure.orm.jpa.*;

import static org.assertj.core.api.Assertions.*;

@RunWith(SpringRunner.class)
@DataJpaTest
public class ExampleRepositoryTests {

	@Autowired
	private TestEntityManager entityManager;

	@Autowired
	private UserRepository repository;

	@Test
	public void testExample() throws Exception {
		this.entityManager.persist(new User("sboot", "1234"));
		User user = this.repository.findByUsername("sboot");
		assertThat(user.getUsername()).isEqualTo("sboot");
		assertThat(user.getVin()).isEqualTo("1234");
	}

}

In-memory embedded databases generally work well for tests, since they are fast and do not require any installation. If, however, you prefer to run tests against a real database you can use the @AutoConfigureTestDatabase annotation, as shown in the following example:

@RunWith(SpringRunner.class)
@DataJpaTest
@AutoConfigureTestDatabase(replace=Replace.NONE)
public class ExampleRepositoryTests {

	// ...

}

43.3.13 Auto-configured JDBC Tests

@JdbcTest is similar to @DataJpaTest but is for tests that only require a DataSource. By default, it configures an in-memory embedded database and a JdbcTemplate. Regular @Component beans are not loaded into the ApplicationContext.

[Tip]Tip

A list of the auto-configurations that are enabled by @JdbcTest can be found in the appendix.

By default, JDBC tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class, as follows:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@RunWith(SpringRunner.class)
@JdbcTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
public class ExampleNonTransactionalTests {

}

If you prefer your test to run against a real database, you can use the @AutoConfigureTestDatabase annotation in the same way as for DataJpaTest. (See "Section 43.3.12, “Auto-configured Data JPA Tests”".)

43.3.14 Auto-configured jOOQ Tests

You can use @JooqTest in a similar fashion as @JdbcTest but for jOOQ-related tests. As jOOQ relies heavily on a Java-based schema that corresponds with the database schema, the existing DataSource is used. If you want to replace it with an in-memory database, you can use @AutoConfigureTestDatabase to override those settings. (For more about using jOOQ with Spring Boot, see "Section 29.5, “Using jOOQ”", earlier in this chapter.) Regular @Component beans are not loaded into the ApplicationContext.

[Tip]Tip

A list of the auto-configurations that are enabled by @JooqTest can be found in the appendix.

@JooqTest configures a DSLContext. Regular @Component beans are not loaded into the ApplicationContext. The following example shows the @JooqTest annotation in use:

import org.jooq.DSLContext;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.jooq.JooqTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@JooqTest
public class ExampleJooqTests {

	@Autowired
	private DSLContext dslContext;
}

JOOQ tests are transactional and roll back at the end of each test by default. If that is not what you want, you can disable transaction management for a test or for the whole test class as shown in the JDBC example.

43.3.15 Auto-configured Data MongoDB Tests

You can use @DataMongoTest to test MongoDB applications. By default, it configures an in-memory embedded MongoDB (if available), configures a MongoTemplate, scans for @Document classes, and configures Spring Data MongoDB repositories. Regular @Component beans are not loaded into the ApplicationContext. (For more about using MongoDB with Spring Boot, see "Section 30.2, “MongoDB”", earlier in this chapter.)

[Tip]Tip

A list of the auto-configuration settings that are enabled by @DataMongoTest can be found in the appendix.

The following class shows the @DataMongoTest annotation in use:

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@DataMongoTest
public class ExampleDataMongoTests {

	@Autowired
	private MongoTemplate mongoTemplate;

	//
}

In-memory embedded MongoDB generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real MongoDB server, you should exclude the embedded MongoDB auto-configuration, as shown in the following example:

import org.junit.runner.RunWith;
 import org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@DataMongoTest(excludeAutoConfiguration = EmbeddedMongoAutoConfiguration.class)
public class ExampleDataMongoNonEmbeddedTests {

}

43.3.16 Auto-configured Data Neo4j Tests

You can use @DataNeo4jTest to test Neo4j applications. By default, it uses an in-memory embedded Neo4j (if the embedded driver is available), scans for @NodeEntity classes, and configures Spring Data Neo4j repositories. Regular @Component beans are not loaded into the ApplicationContext. (For more about using Neo4J with Spring Boot, see "Section 30.3, “Neo4j”", earlier in this chapter.)

[Tip]Tip

A list of the auto-configuration settings that are enabled by @DataNeo4jTest can be found in the appendix.

The following example shows a typical setup for using Neo4J tests in Spring Boot:

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@DataNeo4jTest
public class ExampleDataNeo4jTests {

	@Autowired
	private YourRepository repository;

	//
}

By default, Data Neo4j tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class, as follows:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@RunWith(SpringRunner.class)
@DataNeo4jTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
public class ExampleNonTransactionalTests {

}

43.3.17 Auto-configured Data Redis Tests

You can use @DataRedisTest to test Redis applications. By default, it scans for @RedisHash classes and configures Spring Data Redis repositories. Regular @Component beans are not loaded into the ApplicationContext. (For more about using Redis with Spring Boot, see "Section 30.1, “Redis”", earlier in this chapter.)

[Tip]Tip

A list of the auto-configuration settings that are enabled by @DataRedisTest can be found in the appendix.

The following example shows the @DataRedisTest annotation in use:

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.redis.DataRedisTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@DataRedisTest
public class ExampleDataRedisTests {

	@Autowired
	private YourRepository repository;

	//
}

43.3.18 Auto-configured Data LDAP Tests

You can use @DataLdapTest to test LDAP applications. By default, it configures an in-memory embedded LDAP (if available), configures an LdapTemplate, scans for @Entry classes, and configures Spring Data LDAP repositories. Regular @Component beans are not loaded into the ApplicationContext. (For more about using LDAP with Spring Boot, see "Section 30.9, “LDAP”", earlier in this chapter.)

[Tip]Tip

A list of the auto-configuration settings that are enabled by @DataLdapTest can be found in the appendix.

The following example shows the @DataLdapTest annotation in use:

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
import org.springframework.ldap.core.LdapTemplate;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@DataLdapTest
public class ExampleDataLdapTests {

	@Autowired
	private LdapTemplate ldapTemplate;

	//
}

In-memory embedded LDAP generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real LDAP server, you should exclude the embedded LDAP auto-configuration, as shown in the following example:

import org.junit.runner.RunWith;
import org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@DataLdapTest(excludeAutoConfiguration = EmbeddedLdapAutoConfiguration.class)
public class ExampleDataLdapNonEmbeddedTests {

}

43.3.19 Auto-configured REST Clients

You can use the @RestClientTest annotation to test REST clients. By default, it auto-configures Jackson, GSON, and Jsonb support, configures a RestTemplateBuilder, and adds support for MockRestServiceServer. Regular @Component beans are not loaded into the ApplicationContext.

[Tip]Tip

A list of the auto-configuration settings that are enabled by @RestClientTest can be found in the appendix.

The specific beans that you want to test should be specified by using the value or components attribute of @RestClientTest, as shown in the following example:

@RunWith(SpringRunner.class)
@RestClientTest(RemoteVehicleDetailsService.class)
public class ExampleRestClientTest {

	@Autowired
	private RemoteVehicleDetailsService service;

	@Autowired
	private MockRestServiceServer server;

	@Test
	public void getVehicleDetailsWhenResultIsSuccessShouldReturnDetails()
			throws Exception {
		this.server.expect(requestTo("/greet/details"))
				.andRespond(withSuccess("hello", MediaType.TEXT_PLAIN));
		String greeting = this.service.callRestService();
		assertThat(greeting).isEqualTo("hello");
	}

}

43.3.20 Auto-configured Spring REST Docs Tests

You can use the @AutoConfigureRestDocs annotation to use Spring REST Docs in your tests with Mock MVC or REST Assured. It removes the need for the JUnit rule in Spring REST Docs.

@AutoConfigureRestDocs can be used to override the default output directory (target/generated-snippets if you are using Maven or build/generated-snippets if you are using Gradle). It can also be used to configure the host, scheme, and port that appears in any documented URIs.

Auto-configured Spring REST Docs Tests with Mock MVC

@AutoConfigureRestDocs customizes the MockMvc bean to use Spring REST Docs. You can inject it by using @Autowired and use it in your tests as you normally would when using Mock MVC and Spring REST Docs, as shown in the following example:

import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;

import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;

@RunWith(SpringRunner.class)
@WebMvcTest(UserController.class)
@AutoConfigureRestDocs
public class UserDocumentationTests {

	@Autowired
	private MockMvc mvc;

	@Test
	public void listUsers() throws Exception {
		this.mvc.perform(get("/users").accept(MediaType.TEXT_PLAIN))
				.andExpect(status().isOk())
				.andDo(document("list-users"));
	}

}

If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs, you can use a RestDocsMockMvcConfigurationCustomizer bean, as shown in the following example:

@TestConfiguration
static class CustomizationConfiguration
		implements RestDocsMockMvcConfigurationCustomizer {

	@Override
	public void customize(MockMvcRestDocumentationConfigurer configurer) {
		configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
	}

}

If you want to make use of Spring REST Docs support for a parameterized output directory, you can create a RestDocumentationResultHandler bean. The auto-configuration calls alwaysDo with this result handler, thereby causing each MockMvc call to automatically generate the default snippets. The following example shows a RestDocumentationResultHandler being defined:

@TestConfiguration
static class ResultHandlerConfiguration {

	@Bean
	public RestDocumentationResultHandler restDocumentation() {
		return MockMvcRestDocumentation.document("{method-name}");
	}

}

Auto-configured Spring REST Docs Tests with REST Assured

@AutoConfigureRestDocs makes a RequestSpecification bean, preconfigured to use Spring REST Docs, available to your tests. You can inject it by using @Autowired and use it in your tests as you normally would when using REST Assured and Spring REST Docs, as shown in the following example:

import io.restassured.specification.RequestSpecification;
import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.restdocs.AutoConfigureRestDocs;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.web.server.LocalServerPort;
import org.springframework.test.context.junit4.SpringRunner;

import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.is;
import static org.springframework.restdocs.restassured3.RestAssuredRestDocumentation.document;

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
@AutoConfigureRestDocs
public class UserDocumentationTests {

	@LocalServerPort
	private int port;

	@Autowired
	private RequestSpecification documentationSpec;

	@Test
	public void listUsers() {
		given(this.documentationSpec).filter(document("list-users")).when()
				.port(this.port).get("/").then().assertThat().statusCode(is(200));
	}

}

If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs, a RestDocsRestAssuredConfigurationCustomizer bean can be used, as shown in the following example:

@TestConfiguration
public static class CustomizationConfiguration
		implements RestDocsRestAssuredConfigurationCustomizer {

	@Override
	public void customize(RestAssuredRestDocumentationConfigurer configurer) {
		configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
	}

}

43.3.21 Additional Auto-configuration and Slicing

Each slice provides one or more @AutoConfigure…​ annotations that namely defines the auto-configurations that should be included as part of a slice. Additional auto-configurations can be added by creating a custom @AutoConfigure…​ annotation or simply by adding @ImportAutoConfiguration to the test as shown in the following example:

@RunWith(SpringRunner.class)
@JdbcTest
@ImportAutoConfiguration(IntegrationAutoConfiguration.class)
public class ExampleJdbcTests {

}
[Note]Note

Make sure to not use the regular @Import annotation to import auto-configurations as they are handled in a specific way by Spring Boot.

43.3.22 User Configuration and Slicing

If you structure your code in a sensible way, your @SpringBootApplication class is used by default as the configuration of your tests.

It then becomes important not to litter the application’s main class with configuration settings that are specific to a particular area of its functionality.

Assume that you are using Spring Batch and you rely on the auto-configuration for it. You could define your @SpringBootApplication as follows:

@SpringBootApplication
@EnableBatchProcessing
public class SampleApplication { ... }

Because this class is the source configuration for the test, any slice test actually tries to start Spring Batch, which is definitely not what you want to do. A recommended approach is to move that area-specific configuration to a separate @Configuration class at the same level as your application, as shown in the following example:

@Configuration
@EnableBatchProcessing
public class BatchConfiguration { ... }
[Note]Note

Depending on the complexity of your application, you may either have a single @Configuration class for your customizations or one class per domain area. The latter approach lets you enable it in one of your tests, if necessary, with the @Import annotation.

Another source of confusion is classpath scanning. Assume that, while you structured your code in a sensible way, you need to scan an additional package. Your application may resemble the following code:

@SpringBootApplication
@ComponentScan({ "com.example.app", "org.acme.another" })
public class SampleApplication { ... }

Doing so effectively overrides the default component scan directive with the side effect of scanning those two packages regardless of the slice that you chose. For instance, a @DataJpaTest seems to suddenly scan components and user configurations of your application. Again, moving the custom directive to a separate class is a good way to fix this issue.

[Tip]Tip

If this is not an option for you, you can create a @SpringBootConfiguration somewhere in the hierarchy of your test so that it is used instead. Alternatively, you can specify a source for your test, which disables the behavior of finding a default one.

43.3.23 Using Spock to Test Spring Boot Applications

If you wish to use Spock to test a Spring Boot application, you should add a dependency on Spock’s spock-spring module to your application’s build. spock-spring integrates Spring’s test framework into Spock. It is recommended that you use Spock 1.1 or later to benefit from a number of improvements to Spock’s Spring Framework and Spring Boot integration. See the documentation for Spock’s Spring module for further details.

43.4 Test Utilities

A few test utility classes that are generally useful when testing your application are packaged as part of spring-boot.

43.4.1 ConfigFileApplicationContextInitializer

ConfigFileApplicationContextInitializer is an ApplicationContextInitializer that you can apply to your tests to load Spring Boot application.properties files. You can use it when you do not need the full set of features provided by @SpringBootTest, as shown in the following example:

@ContextConfiguration(classes = Config.class,
	initializers = ConfigFileApplicationContextInitializer.class)
[Note]Note

Using ConfigFileApplicationContextInitializer alone does not provide support for @Value("${…​}") injection. Its only job is to ensure that application.properties files are loaded into Spring’s Environment. For @Value support, you need to either additionally configure a PropertySourcesPlaceholderConfigurer or use @SpringBootTest, which auto-configures one for you.

43.4.2 TestPropertyValues

TestPropertyValues lets you quickly add properties to a ConfigurableEnvironment or ConfigurableApplicationContext. You can call it with key=value strings, as follows:

TestPropertyValues.of("org=Spring", "name=Boot").applyTo(env);

43.4.3 OutputCapture

OutputCapture is a JUnit Rule that you can use to capture System.out and System.err output. You can declare the capture as a @Rule and then use toString() for assertions, as follows:

import org.junit.Rule;
import org.junit.Test;
import org.springframework.boot.test.rule.OutputCapture;

import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;

public class MyTest {

	@Rule
	public OutputCapture capture = new OutputCapture();

	@Test
	public void testName() throws Exception {
		System.out.println("Hello World!");
		assertThat(capture.toString(), containsString("World"));
	}

}

43.4.4 TestRestTemplate

[Tip]Tip

Spring Framework 5.0 provides a new WebTestClient that works for WebFlux integration tests and both WebFlux and MVC end-to-end testing. It provides a fluent API for assertions, unlike TestRestTemplate.

TestRestTemplate is a convenience alternative to Spring’s RestTemplate that is useful in integration tests. You can get a vanilla template or one that sends Basic HTTP authentication (with a username and password). In either case, the template behaves in a test-friendly way by not throwing exceptions on server-side errors. It is recommended, but not mandatory, to use the Apache HTTP Client (version 4.3.2 or better). If you have that on your classpath, the TestRestTemplate responds by configuring the client appropriately. If you do use Apache’s HTTP client, some additional test-friendly features are enabled:

  • Redirects are not followed (so you can assert the response location).
  • Cookies are ignored (so the template is stateless).

TestRestTemplate can be instantiated directly in your integration tests, as shown in the following example:

public class MyTest {

	private TestRestTemplate template = new TestRestTemplate();

	@Test
	public void testRequest() throws Exception {
		HttpHeaders headers = this.template.getForEntity(
				"http://myhost.example.com/example", String.class).getHeaders();
		assertThat(headers.getLocation()).hasHost("other.example.com");
	}

}

Alternatively, if you use the @SpringBootTest annotation with WebEnvironment.RANDOM_PORT or WebEnvironment.DEFINED_PORT, you can inject a fully configured TestRestTemplate and start using it. If necessary, additional customizations can be applied through the RestTemplateBuilder bean. Any URLs that do not specify a host and port automatically connect to the embedded server, as shown in the following example:

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
public class SampleWebClientTests {

	@Autowired
	private TestRestTemplate template;

	@Test
	public void testRequest() {
		HttpHeaders headers = this.template.getForEntity("/example", String.class)
				.getHeaders();
		assertThat(headers.getLocation()).hasHost("other.example.com");
	}

	@TestConfiguration
	static class Config {

		@Bean
		public RestTemplateBuilder restTemplateBuilder() {
			return new RestTemplateBuilder().setConnectTimeout(1000).setReadTimeout(1000);
		}

	}

}