[[features.testing]]
== 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 Jupiter, AssertJ, Hamcrest, and a number of other useful libraries.

[TIP]
====
If you have tests that use JUnit 4, JUnit 5's vintage engine can be used to run them.
To use the vintage engine, add a dependency on `junit-vintage-engine`, as shown in the following example:

[source,xml,indent=0,subs="verbatim"]
----
	<dependency>
		<groupId>org.junit.vintage</groupId>
		<artifactId>junit-vintage-engine</artifactId>
		<scope>test</scope>
		<exclusions>
			<exclusion>
				<groupId>org.hamcrest</groupId>
				<artifactId>hamcrest-core</artifactId>
			</exclusion>
		</exclusions>
	</dependency>
----
====

`hamcrest-core` is excluded in favor of `org.hamcrest:hamcrest` that is part of `spring-boot-starter-test`.



[[features.testing.test-scope-dependencies]]
=== Test Scope Dependencies
The `spring-boot-starter-test` "`Starter`" (in the `test` `scope`) contains the following provided libraries:

* https://junit.org/junit5/[JUnit 5]: The de-facto standard for unit testing Java applications.
* {spring-framework-docs}/testing/integration.html[Spring Test] & Spring Boot Test: Utilities and integration test support for Spring Boot applications.
* https://assertj.github.io/doc/[AssertJ]: A fluent assertion library.
* https://github.com/hamcrest/JavaHamcrest[Hamcrest]: A library of matcher objects (also known as constraints or predicates).
* https://site.mockito.org/[Mockito]: A Java mocking framework.
* https://github.com/skyscreamer/JSONassert[JSONassert]: An assertion library for JSON.
* https://github.com/jayway/JsonPath[JsonPath]: XPath for JSON.
* https://github.com/awaitility/awaitility[Awaitility]: A library for testing asynchronous systems.

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.



[[features.testing.spring-applications]]
=== 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 {spring-framework-docs}/testing.html[relevant section] of the Spring Framework reference documentation.



[[features.testing.spring-boot-applications]]
=== 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: 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 <<features#features.testing.spring-boot-applications.detecting-configuration,creating the `ApplicationContext` used in your tests through `SpringApplication`>>.
In addition to `@SpringBootTest` a number of other annotations are also provided for <<features#features.testing.spring-boot-applications.autoconfigured-tests,testing more specific slices>> of an application.

TIP: If you are using JUnit 4, do not forget to also add `@RunWith(SpringRunner.class)` to your test, otherwise the annotations will be ignored.
If you are using JUnit 5, there is no need to add the equivalent `@ExtendWith(SpringExtension.class)` as `@SpringBootTest` and the other `@...Test` annotations are already annotated with it.

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 <<features#features.testing.spring-boot-applications.with-mock-environment, `@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: 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.

NOTE: `@SpringBootTest` with `webEnvironment = WebEnvironment.RANDOM_PORT` will also start the management server on a separate random port if your application uses a different port for the management server.



[[features.testing.spring-boot-applications.detecting-web-app-type]]
==== Detecting Web Application Type
If Spring MVC is available, a regular MVC-based application context is configured.
If you have only Spring WebFlux, we will 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 configprop:spring.main.web-application-type[] property:

include::code:MyWebFluxTests[]



[[features.testing.spring-boot-applications.detecting-configuration]]
==== 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 <<using#using.structuring-your-code, structured your code>> in a sensible way, your main configuration is usually found.

[NOTE]
====
If you use a <<features#features.testing.spring-boot-applications.autoconfigured-tests, 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 <<features#features.testing.spring-boot-applications.user-configuration-and-slicing, 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: 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.



[[features.testing.spring-boot-applications.using-main]]
==== Using the Test Configuration Main Method
Typically the test configuration discovered by `@SpringBootTest` will be your main `@SpringBootApplication`.
In most well structured applications, this configuration class will also include the `main` method used to launch the application.

For example, the following is a very common code pattern for a typical Spring Boot application:

include::code:typical/MyApplication[]

In the example above, the `main` method doesn't do anything other than delegate to `SpringApplication.run`.
It is, however, possible to have a more complex `main` method that applies customizations before calling `SpringApplication.run`.

For example, here is an application that changes the banner mode and sets additional profiles:

include::code:custom/MyApplication[]

Since customizations in the `main` method can affect the resulting `ApplicationContext`, it's possible that you might also want to use the `main` method to create the `ApplicationContext` used in your tests.
By default, `@SpringBootTest` will not call your `main` method, and instead the class itself is used directly to create the `ApplicationContext`

If you want to change this behavior, you can change the `useMainMethod` attribute of `@SpringBootTest` to `UseMainMethod.ALWAYS` or `UseMainMethod.WHEN_AVAILABLE`.
When set to `ALWAYS`, the test will fail if no `main` method can be found.
When set to `WHEN_AVAILABLE` the `main` method will be used if it is available, otherwise the standard loading mechanism will be used.

For example, the following test will invoke the `main` method of `MyApplication` in order to create the `ApplicationContext`.
If the main method sets additional profiles then those will be active when the `ApplicationContext` starts.

include::code:always/MyApplicationTests[]



[[features.testing.spring-boot-applications.excluding-configuration]]
==== 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 <<features#features.testing.spring-boot-applications.detecting-configuration,have seen earlier>>, `@TestConfiguration` can be used on an inner class of a test to customize the primary configuration.
`@TestConfiguration` can also be used on a top-level class. Doing so indicates that the class should not be picked up by scanning.
You can then import the class explicitly where it is required, as shown in the following example:

include::code:MyTests[]

NOTE: If you directly use `@ComponentScan` (that is, not through `@SpringBootApplication`) you need to register the `TypeExcludeFilter` with it.
See {spring-boot-module-api}/context/TypeExcludeFilter.html[the Javadoc] for details.

NOTE: An imported `@TestConfiguration` is processed earlier than an inner-class `@TestConfiguration` and an imported `@TestConfiguration` will be processed before any configuration found through component scanning.
Generally speaking, this difference in ordering has no noticeable effect but it is something to be aware of if you're relying on bean overriding.



[[features.testing.spring-boot-applications.using-application-arguments]]
==== Using Application Arguments
If your application expects <<features#features.spring-application.application-arguments,arguments>>, you can
have `@SpringBootTest` inject them using the `args` attribute.

include::code:MyApplicationArgumentTests[]



[[features.testing.spring-boot-applications.with-mock-environment]]
==== Testing With a Mock Environment
By default, `@SpringBootTest` does not start the server but instead sets up a mock environment for testing web endpoints.

With Spring MVC, we can query our web endpoints using {spring-framework-docs}/testing/spring-mvc-test-framework.html[`MockMvc`] or `WebTestClient`, as shown in the following example:

include::code:MyMockMvcTests[]

TIP: If you want to focus only on the web layer and not start a complete `ApplicationContext`, consider <<features#features.testing.spring-boot-applications.spring-mvc-tests,using `@WebMvcTest` instead>>.

With Spring WebFlux endpoints, you can use {spring-framework-docs}/testing/webtestclient.html[`WebTestClient`] as shown in the following example:

include::code:MyMockWebTestClientTests[]

[TIP]
====
Testing within a mocked environment is usually faster than running with a full servlet container.
However, since mocking occurs at the Spring MVC layer, code that relies on lower-level servlet container behavior cannot be directly tested with MockMvc.

For example, Spring Boot's error handling is based on the "`error page`" support provided by the servlet container.
This means that, whilst you can test your MVC layer throws and handles exceptions as expected, you cannot directly test that a specific <<web#web.servlet.spring-mvc.error-handling.error-pages, custom error page>> is rendered.
If you need to test these lower-level concerns, you can start a fully running server as described in the next section.
====



[[features.testing.spring-boot-applications.with-running-server]]
==== 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 <<howto#howto.webserver.discover-port,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 {spring-framework-docs}/testing/webtestclient.html[`WebTestClient`], which resolves relative links to the running server and comes with a dedicated API for verifying responses, as shown in the following example:

include::code:MyRandomPortWebTestClientTests[]

TIP: `WebTestClient` can also used with a <<features#features.testing.spring-boot-applications.with-mock-environment, mock environment>>, removing the need for a running server, by annotating your test class with `@AutoConfigureWebTestClient`.

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

include::code:MyRandomPortTestRestTemplateTests[]



[[features.testing.spring-boot-applications.customizing-web-test-client]]
==== Customizing WebTestClient
To customize the `WebTestClient` bean, configure a `WebTestClientBuilderCustomizer` bean.
Any such beans are called with the `WebTestClient.Builder` that is used to create the `WebTestClient`.



[[features.testing.spring-boot-applications.jmx]]
==== 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:

include::code:MyJmxTests[]


[[features.testing.spring-boot-applications.observations]]
==== Using Observations
If you annotate <<features#features.testing.spring-boot-applications.autoconfigured-tests, a sliced test>> with `@AutoConfigureObservability`, it auto-configures an `ObservationRegistry`.



[[features.testing.spring-boot-applications.metrics]]
==== Using Metrics
Regardless of your classpath, meter registries, except the in-memory backed, are not auto-configured when using `@SpringBootTest`.

If you need to export metrics to a different backend as part of an integration test, annotate it with `@AutoConfigureObservability`.

If you annotate <<features#features.testing.spring-boot-applications.autoconfigured-tests, a sliced test>> with `@AutoConfigureObservability`, it auto-configures an in-memory `MeterRegistry`.
Data exporting in sliced tests is not supported with the `@AutoConfigureObservability` annotation.



[[features.testing.spring-boot-applications.tracing]]
==== Using Tracing
Regardless of your classpath, tracing components which are reporting data are not auto-configured when using `@SpringBootTest`.

If you need those components as part of an integration test, annotate the test with `@AutoConfigureObservability`.

If you have created your own reporting components (e.g. a custom `SpanExporter` or `SpanHandler`) and you don't want them to be active in tests, you can use the `@ConditionalOnEnabledTracing` annotation to disable them.

If you annotate <<features#features.testing.spring-boot-applications.autoconfigured-tests, a sliced test>> with `@AutoConfigureObservability`, it auto-configures a no-op `Tracer`.
Data exporting in sliced tests is not supported with the `@AutoConfigureObservability` annotation.



[[features.testing.spring-boot-applications.mocking-beans]]
==== 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]
====
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, listeners must be explicitly added, as shown in the following example:

include::code:listener/MyTests[]
====

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

include::code:bean/MyTests[]

NOTE: `@MockBean` cannot be used to mock the behavior of a bean that is exercised during application context refresh.
By the time the test is executed, the application context refresh has completed and it is too late to configure the mocked behavior.
We recommend using a `@Bean` method to create and configure the mock in this situation.

Additionally, you can use `@SpyBean` to wrap any existing bean with a Mockito `spy`.
See the {spring-boot-test-module-api}/mock/mockito/SpyBean.html[Javadoc] for full details.

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.

TIP: If you are using `@SpyBean` to spy on a bean with `@Cacheable` methods that refer to parameters by name, your application must be compiled with `-parameters`.
This ensures that the parameter names are available to the caching infrastructure once the bean has been spied upon.

TIP: When you are using `@SpyBean` to spy on a bean that is proxied by Spring, you may need to remove Spring's proxy in some situations, for example when setting expectations using `given` or `when`.
Use `AopTestUtils.getTargetObject(yourProxiedSpy)` to do so.



[[features.testing.spring-boot-applications.autoconfigured-tests]]
==== 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: 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`.

NOTE: Including multiple "`slices`" by using several `@...Test` annotations in one test is not supported.
If you need multiple "`slices`", pick one of the `@...Test` annotations and include the `@AutoConfigure...` annotations of the other "`slices`" by hand.

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.



[[features.testing.spring-boot-applications.json-tests]]
==== 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 ``Module``s
* `Gson`
* `Jsonb`

TIP: A list of the auto-configurations that are enabled by `@JsonTest` can be <<test-auto-configuration#appendix.test-auto-configuration,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:

include::code:MyJsonTests[]

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`.

If you use Spring Boot's AssertJ-based helpers to assert on a number value at a given JSON path, you might not be able to use `isEqualTo` depending on the type.
Instead, you can use AssertJ's `satisfies` to assert that the value matches the given condition.
For instance, the following example asserts that the actual number is a float value close to `0.15` within an offset of `0.01`.

include::code:MyJsonAssertJTests[tag=*]



[[features.testing.spring-boot-applications.spring-mvc-tests]]
==== 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`, `HandlerInterceptor`, `WebMvcConfigurer`, `WebMvcRegistrations`, and `HandlerMethodArgumentResolver`.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@WebMvcTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configuration settings that are enabled by `@WebMvcTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

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

include::code:MyControllerTests[]

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

include::code:MyHtmlUnitTests[]

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.

WARNING: The `webDriver` scope created by Spring Boot will replace any user defined scope of the same name.
If you define your own `webDriver` scope you may find it stops working when you use `@WebMvcTest`.

If you have Spring Security on the classpath, `@WebMvcTest` will also scan `WebSecurityConfigurer` beans.
Instead of disabling security completely for such tests, you can use Spring Security's test support.
More details on how to use Spring Security's `MockMvc` support can be found in this _<<howto#howto.testing.with-spring-security>>_ how-to section.

TIP: Sometimes writing Spring MVC tests is not enough; Spring Boot can help you run <<features#features.testing.spring-boot-applications.with-running-server, full end-to-end tests with an actual server>>.



[[features.testing.spring-boot-applications.spring-webflux-tests]]
==== Auto-configured Spring WebFlux Tests
To test that {spring-framework-docs}/web-reactive.html[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`, `WebFilter`, and `WebFluxConfigurer`.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@WebFluxTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configurations that are enabled by `@WebFluxTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

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 {spring-framework-docs}/testing/webtestclient.html[`WebTestClient`], which offers a powerful way to quickly test WebFlux controllers without needing to start a full HTTP server.

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`:

include::code:MyControllerTests[]

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

NOTE: `@WebFluxTest` cannot detect custom security configuration registered as a `@Bean` of type `SecurityWebFilterChain`.
To include that in your test, you will need to import the configuration that registers the bean by using `@Import` or by using `@SpringBootTest`.

TIP: Sometimes writing Spring WebFlux tests is not enough; Spring Boot can help you run <<features#features.testing.spring-boot-applications.with-running-server, full end-to-end tests with an actual server>>.



[[features.testing.spring-boot-applications.spring-graphql-tests]]
==== Auto-configured Spring GraphQL Tests
Spring GraphQL offers a dedicated testing support module; you'll need to add it to your project:

.Maven
[source,xml,indent=0,subs="verbatim"]
----
  <dependencies>
    <dependency>
      <groupId>org.springframework.graphql</groupId>
      <artifactId>spring-graphql-test</artifactId>
      <scope>test</scope>
    </dependency>
    <!-- Unless already present in the compile scope -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-webflux</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>
----

.Gradle
[source,gradle,indent=0,subs="verbatim"]
----
  dependencies {
    testImplementation("org.springframework.graphql:spring-graphql-test")
    // Unless already present in the implementation configuration
    testImplementation("org.springframework.boot:spring-boot-starter-webflux")
  }
----

This testing module ships the {spring-graphql-docs}/#testing-graphqltester[GraphQlTester].
The tester is heavily used in test, so be sure to become familiar with using it.
There are `GraphQlTester` variants and Spring Boot will auto-configure them depending on the type of tests:

* the `ExecutionGraphQlServiceTester` performs tests on the server side, without a client nor a transport
* the `HttpGraphQlTester` performs tests with a client that connects to a server, with or without a live server

Spring Boot helps you to test your {spring-graphql-docs}/#controllers[Spring GraphQL Controllers] with the `@GraphQlTest` annotation.
`@GraphQlTest` auto-configures the Spring GraphQL infrastructure, without any transport nor server being involved.
This limits scanned beans to `@Controller`, `RuntimeWiringConfigurer`, `JsonComponent`, `Converter`, `GenericConverter`, `DataFetcherExceptionResolver`, `Instrumentation` and `GraphQlSourceBuilderCustomizer`.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@GraphQlTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configurations that are enabled by `@GraphQlTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

Often, `@GraphQlTest` is limited to a set of controllers and used in combination with the `@MockBean` annotation to provide mock implementations for required collaborators.

include::code:GreetingControllerTests[]

`@SpringBootTest` tests are full integration tests and involve the entire application.
When using a random or defined port, a live server is configured and an `HttpGraphQlTester` bean is contributed automatically so you can use it to test your server.
When a MOCK environment is configured, you can also request an `HttpGraphQlTester` bean by annotating your test class with `@AutoConfigureHttpGraphQlTester`:

include::code:GraphQlIntegrationTests[]



[[features.testing.spring-boot-applications.autoconfigured-spring-data-cassandra]]
==== Auto-configured Data Cassandra Tests
You can use `@DataCassandraTest` to test Cassandra applications.
By default, it configures a `CassandraTemplate`, scans for `@Table` classes, and configures Spring Data Cassandra repositories.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataCassandraTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
(For more about using Cassandra with Spring Boot, see "<<data#data.nosql.cassandra>>".)

TIP: A list of the auto-configuration settings that are enabled by `@DataCassandraTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

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

include::code:MyDataCassandraTests[]



[[features.testing.spring-boot-applications.autoconfigured-spring-data-couchbase]]
==== Auto-configured Data Couchbase Tests
You can use `@DataCouchbaseTest` to test Couchbase applications.
By default, it configures a `CouchbaseTemplate` or `ReactiveCouchbaseTemplate`, scans for `@Document` classes, and configures Spring Data Couchbase repositories.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataCouchbaseTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
(For more about using Couchbase with Spring Boot, see "<<data#data.nosql.couchbase>>", earlier in this chapter.)

TIP: A list of the auto-configuration settings that are enabled by `@DataCouchbaseTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

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

include::code:MyDataCouchbaseTests[]



[[features.testing.spring-boot-applications.autoconfigured-spring-data-elasticsearch]]
==== Auto-configured Data Elasticsearch Tests
You can use `@DataElasticsearchTest` to test Elasticsearch applications.
By default, it configures an `ElasticsearchRestTemplate`, scans for `@Document` classes, and configures Spring Data Elasticsearch repositories.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataElasticsearchTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
(For more about using Elasticsearch with Spring Boot, see "<<data#data.nosql.elasticsearch>>", earlier in this chapter.)

TIP: A list of the auto-configuration settings that are enabled by `@DataElasticsearchTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

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

include::code:MyDataElasticsearchTests[]



[[features.testing.spring-boot-applications.autoconfigured-spring-data-jpa]]
==== Auto-configured Data JPA Tests
You can use the `@DataJpaTest` annotation to test JPA applications.
By default, it scans for `@Entity` classes and configures Spring Data JPA repositories.
If an embedded database is available on the classpath, it configures one as well.
SQL queries are logged by default by setting the `spring.jpa.show-sql` property to `true`.
This can be disabled using the `showSql` attribute of the annotation.

Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataJpaTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configuration settings that are enabled by `@DataJpaTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

By default, data JPA tests are transactional and roll back at the end of each test.
See the {spring-framework-docs}/testing/testcontext-framework/tx.html#testcontext-tx-enabling-transactions[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:

include::code:MyNonTransactionalTests[]

Data JPA tests may also inject a {spring-boot-test-autoconfigure-module-code}/orm/jpa/TestEntityManager.java[`TestEntityManager`] bean, which provides an alternative to the standard JPA `EntityManager` that is specifically designed for tests.

TIP: `TestEntityManager` can also be auto-configured to any of your Spring-based test class by adding `@AutoConfigureTestEntityManager`.
When doing so, make sure that your test is running in a transaction, for instance by adding  `@Transactional` on your test class or method.

A `JdbcTemplate` is also available if you need that.
The following example shows the `@DataJpaTest` annotation in use:

include::code:withoutdb/MyRepositoryTests[]

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:

include::code:withdb/MyRepositoryTests[]



[[features.testing.spring-boot-applications.autoconfigured-jdbc]]
==== Auto-configured JDBC Tests
`@JdbcTest` is similar to `@DataJpaTest` but is for tests that only require a `DataSource` and do not use Spring Data JDBC.
By default, it configures an in-memory embedded database and a `JdbcTemplate`.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@JdbcTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configurations that are enabled by `@JdbcTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

By default, JDBC tests are transactional and roll back at the end of each test.
See the {spring-framework-docs}/testing/testcontext-framework/tx.html#testcontext-tx-enabling-transactions[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:

include::code:MyTransactionalTests[]

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 "<<features#features.testing.spring-boot-applications.autoconfigured-spring-data-jpa>>".)



[[features.testing.spring-boot-applications.autoconfigured-spring-data-jdbc]]
==== Auto-configured Data JDBC Tests
`@DataJdbcTest` is similar to `@JdbcTest` but is for tests that use Spring Data JDBC repositories.
By default, it configures an in-memory embedded database, a `JdbcTemplate`, and Spring Data JDBC repositories.
Only `AbstractJdbcConfiguration` subclasses are scanned when the `@DataJdbcTest` annotation is used, regular `@Component` and `@ConfigurationProperties` beans are not scanned.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configurations that are enabled by `@DataJdbcTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

By default, Data JDBC tests are transactional and roll back at the end of each test.
See the {spring-framework-docs}/testing/testcontext-framework/tx.html#testcontext-tx-enabling-transactions[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 test class as <<features#features.testing.spring-boot-applications.autoconfigured-jdbc,shown in the JDBC example>>.

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 "<<features#features.testing.spring-boot-applications.autoconfigured-spring-data-jpa>>".)



[[features.testing.spring-boot-applications.autoconfigured-spring-data-r2dbc]]
==== Auto-configured Data R2DBC Tests
`@DataR2dbcTest` is similar to `@DataJdbcTest` but is for tests that use Spring Data R2DBC repositories.
By default, it configures an in-memory embedded database, an `R2dbcEntityTemplate`, and Spring Data R2DBC repositories.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataR2dbcTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configurations that are enabled by `@DataR2dbcTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

By default, Data R2DBC tests are not transactional.

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 "<<features#features.testing.spring-boot-applications.autoconfigured-spring-data-jpa>>".)



[[features.testing.spring-boot-applications.autoconfigured-jooq]]
==== 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 "<<data#data.sql.jooq>>".)
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@JooqTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configurations that are enabled by `@JooqTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

`@JooqTest` configures a `DSLContext`.
The following example shows the `@JooqTest` annotation in use:

include::code:MyJooqTests[]

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 <<features#features.testing.spring-boot-applications.autoconfigured-jdbc,shown in the JDBC example>>.



[[features.testing.spring-boot-applications.autoconfigured-spring-data-mongodb]]
==== Auto-configured Data MongoDB Tests
You can use `@DataMongoTest` to test MongoDB applications.
By default, it configures a `MongoTemplate`, scans for `@Document` classes, and configures Spring Data MongoDB repositories.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataMongoTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
(For more about using MongoDB with Spring Boot, see "<<data#data.nosql.mongodb>>".)

TIP: A list of the auto-configuration settings that are enabled by `@DataMongoTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

The following class shows the `@DataMongoTest` annotation in use:

include::code:MyDataMongoDbTests[]



[[features.testing.spring-boot-applications.autoconfigured-spring-data-neo4j]]
==== Auto-configured Data Neo4j Tests
You can use `@DataNeo4jTest` to test Neo4j applications.
By default, it scans for `@Node` classes, and configures Spring Data Neo4j repositories.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataNeo4jTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
(For more about using Neo4J with Spring Boot, see "<<data#data.nosql.neo4j>>".)

TIP: A list of the auto-configuration settings that are enabled by `@DataNeo4jTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

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

include::code:propagation/MyDataNeo4jTests[]

By default, Data Neo4j tests are transactional and roll back at the end of each test.
See the {spring-framework-docs}/testing/testcontext-framework/tx.html#testcontext-tx-enabling-transactions[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:

include::code:nopropagation/MyDataNeo4jTests[]

NOTE: Transactional tests are not supported with reactive access.
If you are using this style, you must configure `@DataNeo4jTest` tests as described above.



[[features.testing.spring-boot-applications.autoconfigured-spring-data-redis]]
==== 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` and `@ConfigurationProperties` beans are not scanned when the `@DataRedisTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
(For more about using Redis with Spring Boot, see "<<data#data.nosql.redis>>".)

TIP: A list of the auto-configuration settings that are enabled by `@DataRedisTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

The following example shows the `@DataRedisTest` annotation in use:

include::code:MyDataRedisTests[]



[[features.testing.spring-boot-applications.autoconfigured-spring-data-ldap]]
==== 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` and `@ConfigurationProperties` beans are not scanned when the `@DataLdapTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
(For more about using LDAP with Spring Boot, see "<<data#data.nosql.ldap>>".)

TIP: A list of the auto-configuration settings that are enabled by `@DataLdapTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

The following example shows the `@DataLdapTest` annotation in use:

include::code:inmemory/MyDataLdapTests[]

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:

include::code:server/MyDataLdapTests[]



[[features.testing.spring-boot-applications.autoconfigured-rest-client]]
==== 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 a `RestClient.Builder`, and adds support for `MockRestServiceServer`.
Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@RestClientTest` annotation is used.
`@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.

TIP: A list of the auto-configuration settings that are enabled by `@RestClientTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

The specific beans that you want to test should be specified by using the `value` or `components` attribute of `@RestClientTest`.

When using a `RestTemplateBuilder` in the beans under test and `RestTemplateBuilder.rootUri(String rootUri)` has been called when building the `RestTemplate`, then the root URI should be omitted from the `MockRestServiceServer` expectations as shown in the following example:

include::code:MyRestTemplateServiceTests[]

When using a `RestClient.Builder` in the beans under test, or when using a `RestTemplateBuilder` without calling `rootUri(String rootURI)`, the full URI must be used in the `MockRestServiceServer` expectations as shown in the following example:

include::code:MyRestClientServiceTests[]



[[features.testing.spring-boot-applications.autoconfigured-spring-restdocs]]
==== Auto-configured Spring REST Docs Tests
You can use the `@AutoConfigureRestDocs` annotation to use {spring-restdocs}[Spring REST Docs] in your tests with Mock MVC, REST Assured, or WebTestClient.
It removes the need for the JUnit extension 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.



[[features.testing.spring-boot-applications.autoconfigured-spring-restdocs.with-mock-mvc]]
===== Auto-configured Spring REST Docs Tests With Mock MVC
`@AutoConfigureRestDocs` customizes the `MockMvc` bean to use Spring REST Docs when testing servlet-based web applications.
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:

include::code:MyUserDocumentationTests[]

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:

include::code:MyRestDocsConfiguration[]

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:

include::code:MyResultHandlerConfiguration[]



[[features.testing.spring-boot-applications.autoconfigured-spring-restdocs.with-web-test-client]]
===== Auto-configured Spring REST Docs Tests With WebTestClient
`@AutoConfigureRestDocs` can also be used with `WebTestClient` when testing reactive web applications.
You can inject it by using `@Autowired` and use it in your tests as you normally would when using `@WebFluxTest` and Spring REST Docs, as shown in the following example:

include::code:MyUsersDocumentationTests[]

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

include::code:MyRestDocsConfiguration[]

If you want to make use of Spring REST Docs support for a parameterized output directory, you can use a `WebTestClientBuilderCustomizer` to configure a consumer for every entity exchange result.
The following example shows such a `WebTestClientBuilderCustomizer` being defined:

include::code:MyWebTestClientBuilderCustomizerConfiguration[]



[[features.testing.spring-boot-applications.autoconfigured-spring-restdocs.with-rest-assured]]
===== 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:

include::code:MyUserDocumentationTests[]

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:

include::code:MyRestDocsConfiguration[]



[[features.testing.spring-boot-applications.autoconfigured-webservices]]
==== Auto-configured Spring Web Services Tests



[[features.testing.spring-boot-applications.autoconfigured-webservices.client]]
===== Auto-configured Spring Web Services Client Tests
You can use `@WebServiceClientTest` to test applications that call web services using the Spring Web Services project.
By default, it configures a mock `WebServiceServer` bean and automatically customizes your `WebServiceTemplateBuilder`.
(For more about using Web Services with Spring Boot, see "<<io#io.webservices>>".)


TIP: A list of the auto-configuration settings that are enabled by `@WebServiceClientTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

The following example shows the `@WebServiceClientTest` annotation in use:

include::code:MyWebServiceClientTests[]



[[features.testing.spring-boot-applications.autoconfigured-webservices.server]]
===== Auto-configured Spring Web Services Server Tests
You can use `@WebServiceServerTest` to test applications that implement web services using the Spring Web Services project.
By default, it configures a `MockWebServiceClient` bean that can be used to call your web service endpoints.
(For more about using Web Services with Spring Boot, see "<<io#io.webservices>>".)


TIP: A list of the auto-configuration settings that are enabled by `@WebServiceServerTest` can be <<test-auto-configuration#appendix.test-auto-configuration,found in the appendix>>.

The following example shows the `@WebServiceServerTest` annotation in use:

include::code:MyWebServiceServerTests[]



[[features.testing.spring-boot-applications.additional-autoconfiguration-and-slicing]]
==== 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 on a test-by-test basis by creating a custom `@AutoConfigure...` annotation or by adding `@ImportAutoConfiguration` to the test as shown in the following example:

include::code:MyJdbcTests[]

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.

Alternatively, additional auto-configurations can be added for any use of a slice annotation by registering them in a file stored in `META-INF/spring` as shown in the following example:

.META-INF/spring/org.springframework.boot.test.autoconfigure.jdbc.JdbcTest.imports
[indent=0]
----
	com.example.IntegrationAutoConfiguration
----

In this example, the `com.example.IntegrationAutoConfiguration` is enabled on every test annotated with `@JdbcTest`.

TIP: You can use comments with `#` in this file.

TIP: A slice or `@AutoConfigure...` annotation can be customized this way as long as it is meta-annotated with `@ImportAutoConfiguration`.



[[features.testing.spring-boot-applications.user-configuration-and-slicing]]
==== User Configuration and Slicing
If you <<using#using.structuring-your-code, structure your code>> in a sensible way, your `@SpringBootApplication` class is <<features#features.testing.spring-boot-applications.detecting-configuration, 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 Data MongoDB, you rely on the auto-configuration for it, and you have enabled auditing.
You could define your `@SpringBootApplication` as follows:

include::code:MyApplication[]

Because this class is the source configuration for the test, any slice test actually tries to enable Mongo auditing, 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:

include::code:MyMongoConfiguration[]

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.
See <<howto#howto.testing.slice-tests,this how-to section>> for more details on when you might want to enable specific `@Configuration` classes for slice tests.

Test slices exclude `@Configuration` classes from scanning.
For example, for a `@WebMvcTest`, the following configuration will not include the given `WebMvcConfigurer` bean in the application context loaded by the test slice:

include::code:MyWebConfiguration[]

The configuration below will, however, cause the custom `WebMvcConfigurer` to be loaded by the test slice.

include::code:MyWebMvcConfigurer[]

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:

include::code:scan/MyApplication[]

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: 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.



[[features.testing.spring-boot-applications.spock]]
==== Using Spock to Test Spring Boot Applications
Spock 2.2 or later can be used to test a Spring Boot application.
To do so, add a dependency on a `-groovy-4.0` version of Spock's `spock-spring` module to your application's build.
`spock-spring` integrates Spring's test framework into Spock.
See https://spockframework.org/spock/docs/2.2-M1/modules.html#_spring_module[the documentation for Spock's Spring module] for further details.



[[features.testing.testcontainers]]
=== Testcontainers
The https://www.testcontainers.org/[Testcontainers] library provides a way to manage services running inside Docker containers.
It integrates with JUnit, allowing you to write a test class that can start up a container before any of the tests run.
Testcontainers is especially useful for writing integration tests that talk to a real backend service such as MySQL, MongoDB, Cassandra and others.

Testcontainers can be used in a Spring Boot test as follows:

include::code:vanilla/MyIntegrationTests[]

This will start up a docker container running Neo4j (if Docker is running locally) before any of the tests are run.
In most cases, you will need to configure the application to connect to the service running in the container.



[[features.testing.testcontainers.service-connections]]
==== Service Connections
A service connection is a connection to any remote service.
Spring Boot's auto-configuration can consume the details of a service connection and use them to establish a connection to a remote service.
When doing so, the connection details take precedence over any connection-related configuration properties.

When using Testcontainers, connection details can be automatically created for a service running in a container by annotating the container field in the test class.

include::code:MyIntegrationTests[]

Thanks to `@ServiceConnection`, the above configuration allows Neo4j-related beans in the application to communicate with Neo4j running inside the Testcontainers-managed Docker container.
This is done by automatically defining a `Neo4jConnectionDetails` bean which is then used by the Neo4j auto-configuration, overriding any connection-related configuration properties.

NOTE: You'll need to add the `spring-boot-testcontainers` module as a test dependency in order to use service connections with Testcontainers.

Service connection annotations are processed by `ContainerConnectionDetailsFactory` classes registered with `spring.factories`.
A `ContainerConnectionDetailsFactory` can create a `ConnectionDetails` bean based on a specific `Container` subclass, or the Docker image name.

The following service connection factories are provided in the `spring-boot-testcontainers` jar:

|===
| Connection Details | Matched on

| `ActiveMQConnectionDetails`
| Containers named "symptoma/activemq"

| `CassandraConnectionDetails`
| Containers of type `CassandraContainer`

| `CouchbaseConnectionDetails`
| Containers of type `CouchbaseContainer`

| `ElasticsearchConnectionDetails`
| Containers of type `ElasticsearchContainer`

| `FlywayConnectionDetails`
| Containers of type `JdbcDatabaseContainer`

| `JdbcConnectionDetails`
| Containers of type `JdbcDatabaseContainer`

| `KafkaConnectionDetails`
| Containers of type `org.testcontainers.containers.KafkaContainer` or `RedpandaContainer`

| `LiquibaseConnectionDetails`
| Containers of type `JdbcDatabaseContainer`

| `MongoConnectionDetails`
| Containers of type `MongoDBContainer`

| `Neo4jConnectionDetails`
| Containers of type `Neo4jContainer`

| `OtlpMetricsConnectionDetails`
| Containers named "otel/opentelemetry-collector-contrib"

| `OtlpTracingConnectionDetails`
| Containers named "otel/opentelemetry-collector-contrib"

| `PulsarConnectionDetails`
| Containers of type `PulsarContainer`

| `R2dbcConnectionDetails`
| Containers of type `MariaDBContainer`, `MSSQLServerContainer`, `MySQLContainer`, `OracleContainer`, or `PostgreSQLContainer`

| `RabbitConnectionDetails`
| Containers of type `RabbitMQContainer`

| `RedisConnectionDetails`
| Containers named "redis"

| `ZipkinConnectionDetails`
| Containers named "openzipkin/zipkin"
|===

[TIP]
====
By default all applicable connection details beans will be created for a given `Container`.
For example, a `PostgreSQLContainer` will create both `JdbcConnectionDetails` and `R2dbcConnectionDetails`.

If you want to create only a subset of the applicable types, you can use the `type` attribute of `@ServiceConnection`.
====

By default `Container.getDockerImageName().getRepository()` is used to obtain the name used to find connection details.
The repository portion of the Docker image name ignores any registry and the version.
This works as long as Spring Boot is able to get the instance of the `Container`, which is the case when using a `static` field like in the example above.

If you're using a `@Bean` method, Spring Boot won't call the bean method to get the Docker image name, because this would cause eager initialization issues.
Instead, the return type of the bean method is used to find out which connection detail should be used.
This works as long as you're using typed containers, e.g. `Neo4jContainer` or `RabbitMQContainer`.
This stops working if you're using `GenericContainer`, e.g. with Redis, as shown in the following example:

include::code:MyRedisConfiguration[]

Spring Boot can't tell from `GenericContainer` which container image is used, so the `name` attribute from `@ServiceConnection` must be used to provide that hint.

You can also can use the `name` attribute of `@ServiceConnection` to override which connection detail will be used, for example when using custom images.
If you are using the Docker image `registry.mycompany.com/mirror/myredis`, you'd use `@ServiceConnection(name="redis")` to ensure `RedisConnectionDetails` are created.



[[features.testing.testcontainers.dynamic-properties]]
==== Dynamic Properties
A slightly more verbose but also more flexible alternative to service connections is `@DynamicPropertySource`.
A static `@DynamicPropertySource` method allows adding dynamic property values to the Spring Environment.

include::code:MyIntegrationTests[]

The above configuration allows Neo4j-related beans in the application to communicate with Neo4j running inside the Testcontainers-managed Docker container.



[[features.testing.utilities]]
=== Test Utilities
A few test utility classes that are generally useful when testing your application are packaged as part of `spring-boot`.



[[features.testing.utilities.config-data-application-context-initializer]]
==== ConfigDataApplicationContextInitializer
`ConfigDataApplicationContextInitializer` 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:

include::code:MyConfigFileTests[]

NOTE: Using `ConfigDataApplicationContextInitializer` 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.



[[features.testing.utilities.test-property-values]]
==== TestPropertyValues
`TestPropertyValues` lets you quickly add properties to a `ConfigurableEnvironment` or `ConfigurableApplicationContext`.
You can call it with `key=value` strings, as follows:

include::code:MyEnvironmentTests[]



[[features.testing.utilities.output-capture]]
==== OutputCapture
`OutputCapture` is a JUnit `Extension` that you can use to capture `System.out` and `System.err` output.
To use it, add `@ExtendWith(OutputCaptureExtension.class)` and inject `CapturedOutput` as an argument to your test class constructor or test method as follows:

include::code:MyOutputCaptureTests[]



[[features.testing.utilities.test-rest-template]]
==== 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 is fault tolerant.
This means that it behaves in a test-friendly way by not throwing exceptions on 4xx and 5xx errors.
Instead, such errors can be detected through the returned `ResponseEntity` and its status code.

TIP: Spring Framework 5.0 provides a new `WebTestClient` that works for <<features#features.testing.spring-boot-applications.spring-webflux-tests, WebFlux integration tests>> and both <<features#features.testing.spring-boot-applications.with-running-server, WebFlux and MVC end-to-end testing>>.
It provides a fluent API for assertions, unlike `TestRestTemplate`.

It is recommended, but not mandatory, to use the Apache HTTP Client (version 5.1 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:

include::code:MyTests[]

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:

include::code:MySpringBootTests[]
