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 will just use the spring-boot-starter-test ‘Starter’ which imports both Spring Boot test modules as well has JUnit, AssertJ, Hamcrest and a number of other useful libraries.

Test scope dependencies

If you use the spring-boot-starter-test ‘Starter’ (in the test scope), you will find 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.

By default, Spring Boot uses Mockito 1.x. However it’s also possible to use 2.x if you wish.

These are common libraries that we generally find useful when writing tests. You are free to add additional test dependencies of your own if these don’t suit your needs.

Testing Spring applications

One of the major advantages of dependency injection is that it should make your code easier to unit test. You can simply instantiate objects 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 actually involved in the process). It’s 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 just 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.

Testing Spring Boot applications

A Spring Boot application is just 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. One thing to watch out for though is that the external properties, logging and other features of Spring Boot are only installed in the context by default 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 via SpringApplication. In addition to @SpringBootTest a number of other annotations are also provided for testing more specific slices of an application.

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

You can use the webEnvironment attribute of @SpringBootTest to further refine how your tests will run:

  • MOCK — Loads a WebApplicationContext and provides a mock servlet environment. Embedded servlet containers are not started when using this annotation. If servlet APIs are not on your classpath this mode will transparently fallback to creating a regular non-web ApplicationContext. Can be used in conjunction with @AutoConfigureMockMvc for MockMvc-based testing of your application.

  • RANDOM_PORT — Loads an EmbeddedWebApplicationContext and provides a real servlet environment. Embedded servlet containers are started and listening on a random port.

  • DEFINED_PORT — Loads an EmbeddedWebApplicationContext and provides a real servlet environment. Embedded servlet containers are started and listening on a defined port (i.e from your application.properties or on the default port 8080).

  • NONE — Loads an ApplicationContext using SpringApplication but does not provide any servlet environment (mock or otherwise).

If your test is @Transactional, it will rollback 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, HTTP client and server will run in separate threads, thus separate transactions. Any transaction initiated on the server won’t rollback in this case.

Detecting test configuration

If you’re 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 will search for your primary configuration automatically whenever you don’t explicitly define one.

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

If you use a test annotation to test a more specific slice of your application with such setup, you should avoid adding configuration that are specific to a particular area on the main’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-annoted 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 a your application’s primary configuration, a nested @TestConfiguration class will be used in addition to your application’s primary configuration.

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

Excluding test configuration

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

As we have seen above, @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:

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

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

}
If you directly use @ComponentScan (i.e. not via @SpringBootApplication) you will need to register the TypeExcludeFilter with it. See the Javadoc for details.

Working with random ports

If you need to start a full running server for tests, we recommend that you use random ports. If you use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) an available port will be 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 TestRestTemplate which will resolve relative links to the running server.

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 RandomPortExampleTests {

	@Autowired
	private TestRestTemplate restTemplate;

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

}

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() {
		// ...
	}

}

Mocking and spying beans

It’s sometimes necessary to mock certain components within your application context when running tests. For example, you may have a facade over some remote service that’s 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 will also be injected. Mock beans are automatically reset after each test method.

This feature is automatically enabled as long as your test uses one of Spring Boot’s test annotations (i.e. @SpringBootTest). To use this feature with a different arrangement, a listener will need to be added explicitly:

@TestExecutionListeners(MockitoTestExecutionListener.class)

Here’s a typical example where we replace 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 also use @SpyBean to wrap any existing bean with a Mockito spy. See the Javadoc for full details.

Auto-configured tests

Spring Boot’s auto-configuration system works well for applications, but can sometimes be a little too much for tests. It’s often helpful 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 don’t want to involve database calls in those tests; or you might be wanting to test JPA entities, and you’re not interested in 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.

Each slice 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.
It’s also possible to use the @AutoConfigure…​ annotations with the standard @SpringBootTest annotation. You can use this combination if you’re not interested in ‘slicing’ your application but you want some of the auto-configured test beans.

Auto-configured JSON tests

To test that Object JSON serialization and deserialization is working as expected you can use the @JsonTest annotation. @JsonTest will auto-configure Jackson ObjectMapper, any @JsonComponent beans and any Jackson Modules. It also configures Gson if you happen to be using that instead of, or as well as, Jackson. 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 is as expected. The JacksonTester, GsonTester and BasicJsonTester classes can be used for Jackson, Gson and Strings respectively. Any helper fields on the test class can be @Autowired when using @JsonTest.

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");
	}

}
JSON helper classes can also be used directly in standard unit tests. Simply call the initFields method of the helper in your @Before method if you aren’t using @JsonTest.

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

Auto-configured Spring MVC tests

To test Spring MVC controllers are working as expected you can use the @WebMvcTest annotation. @WebMvcTest will auto-configure the Spring MVC infrastructure and limit scanned beans to @Controller, @ControllerAdvice, @JsonComponent, Filter, WebMvcConfigurer and HandlerMethodArgumentResolver. Regular @Component beans will not be scanned when using this annotation.

Often @WebMvcTest will be limited to a single controller and 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.

You can also auto-configure MockMvc in a non-@WebMvcTest (e.g. SpringBootTest) by annotating it with @AutoConfigureMockMvc. 
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"));
	}

}
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 will also provide a WebClient bean and/or a WebDriver bean. Here is an example that uses HtmlUnit:

import com.gargoylesoftware.htmlunit.*;
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.html");
		assertThat(page.getBody().getTextContent()).isEqualTo("Honda Civic");
	}

}
By default Spring Boot will put WebDriver beans in a special “scope” to ensure that the driver is quit after each test, and that a new instance is injected. If you don’t want this behavior you can add @Scope("singleton") to your WebDriver @Bean definition.

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

Auto-configured Data JPA tests

@DataJpaTest can be used if you want to test JPA applications. By default it will configure an in-memory embedded database, scan for @Entity classes and configure Spring Data JPA repositories. Regular @Component beans will not be loaded into the ApplicationContext.

Data JPA tests are transactional and rollback at the end of each test by default, see the relevant section in the Spring Reference Documentation for more details. If that’s 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 specifically designed for tests. If you want to use TestEntityManager outside of @DataJpaTests you can also use the @AutoConfigureTestEntityManager annotation. A JdbcTemplate is also available if you need that.

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 don’t require any developer installation. If, however, you prefer to run tests against a real database you can use the @AutoConfigureTestDatabase annotation:

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

	// ...

}

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

Auto-configured JDBC tests

@JdbcTest is similar to @DataJpaTest but for pure jdbc-related tests. By default it will also configure an in-memory embedded database and a JdbcTemplate. Regular @Component beans will not be loaded into the ApplicationContext.

JDBC tests are transactional and rollback at the end of each test by default, see the relevant section in the Spring Reference Documentation for more details. If that’s 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 the same way as for DataJpaTest.

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

Auto-configured Data MongoDB tests

@DataMongoTest can be used if you want to test MongoDB applications. By default, it will configure an in-memory embedded MongoDB (if available), configure a MongoTemplate, scan for @Document classes and configure Spring Data MongoDB repositories. Regular @Component beans will not be loaded into the ApplicationContext:

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 doesn’t require any developer installation. If, however, you prefer to run tests against a real MongoDB server you should exclude the embedded MongoDB auto-configuration:

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 {

}

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

Auto-configured REST clients

The @RestClientTest annotation can be used if you want to test REST clients. By default it will auto-configure Jackson and GSON support, configure a RestTemplateBuilder and add support for MockRestServiceServer. The specific beans that you want to test should be specified using value or components attribute of @RestClientTest:

@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");
	}

}

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

Auto-configured Spring REST Docs tests

The @AutoConfigureRestDocs annotation can be used if you want to use Spring REST Docs in your tests. It will automatically configure MockMvc to use Spring REST Docs and remove the need for Spring REST Docs' JUnit rule.

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("target/generated-snippets")
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"));
	}

}

In addition to configuring the output directory, @AutoConfigureRestDocs can also configure the host, scheme, and port that will appear in any documented URIs. If you require more control over Spring REST Docs' configuration a RestDocsMockMvcConfigurationCustomizer bean can be used:

@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 will call alwaysDo with this result handler, thereby causing each MockMvc call to automatically generate the default snippets:

@TestConfiguration
static class ResultHandlerConfiguration {

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

}

User configuration and slicing

If you’ve structured 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 that are are specific to a particular area of its functionality.

Let’s assume that you are using Spring Batch and you’re relying on the auto-configuration for it. Your could define your @SpringBootApplication as follows:

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

Because this class is the source configuration for the test, any slice test will actually attempt 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.

@Configuration
@EnableBatchProcessing
public class BatchConfiguration { ... }
Depending on the surface area of your application, you may either have a single ApplicationConfiguration class for your customizations or one class per domain area when it makes sense. The latter approach allows you to enable it in one of your test if necessary via @Import.

Another source of confusion is classpath scanning. Let’s assume that, while you’ve structured your code in a sensible way, you need to scan an additional package. Your application may look like this:

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

This effectively overrides the default component scan directive with the side effect of scanning those two packages regardless of the slice that you’ve chosen. For instance a @DataJpaTest will all of a sudden 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.

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. Or you can specify a source for your test which will disable the behaviour of finding a default one.

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. Exactly how you can use Spock to test a Spring Boot application depends on the version of Spock that you are using.

Spring Boot provides dependency management for Spock 1.0. If you wish to use Spock 1.1 you should override the spock.version property in your build.gradle or pom.xml file.

When using Spock 1.1, the annotations described above can be used and you can annotate your Specification with @SpringBootTest to suit the needs of your tests. When using Spock 1.0, @SpringBootTest will not work for a web project. If you wish to use Spock to test a web project, you should use Spock 1.1 by overriding the spock.version property as described above.

Test utilities

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

ConfigFileApplicationContextInitializer

ConfigFileApplicationContextInitializer is an ApplicationContextInitializer that can apply to your tests to load Spring Boot application.properties files. You can use this when you don’t need the full features provided by @SpringBootTest.

@ContextConfiguration(classes = Config.class,
	initializers = ConfigFileApplicationContextInitializer.class)
Using ConfigFileApplicationContextInitializer alone won’t 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 where one will be auto-configured for you.

EnvironmentTestUtils

EnvironmentTestUtils allows you to quickly add properties to a ConfigurableEnvironment or ConfigurableApplicationContext. Simply call it with key=value strings:

EnvironmentTestUtils.addEnvironment(env, "org=Spring", "name=Boot");

OutputCapture

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

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"));
	}

}

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 will behave in a test-friendly way by not throwing exceptions on server-side errors. It is recommended, but not mandatory, to use Apache HTTP Client (version 4.3.2 or better), and if you have that on your classpath the TestRestTemplate will respond by configuring the client appropriately. If you do use Apache’s HTTP client some additional test-friendly features will be enabled:

  • Redirects will not be followed (so you can assert the response location)

  • Cookies will be ignored (so the template is stateless)

TestRestTemplate can be instantiated directly in your integration tests:

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 are using the @SpringBootTest annotation with WebEnvironment.RANDOM_PORT or WebEnvironment.DEFINED_PORT, you can just inject a fully configured TestRestTemplate and start using it. If necessary, additional customizations can be applied via the RestTemplateBuilder bean. Any URLs that do not specify a host and port will automatically connect to the embedded server:

@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);
		}

	}

}