If you use the spring-boot-starter-test ‘Starter POM’ (in the test scope), you will find the following provided libraries:

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.

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 POM’ 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.

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 @SpringApplicationConfiguration annotation as an alternative to the standard spring-test @ContextConfiguration annotation. If you use @SpringApplicationConfiguration to configure the ApplicationContext used in your tests, it will be created via SpringApplication and you will get the additional Spring Boot features.

For example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SampleDataJpaApplication.class)
public class CityRepositoryIntegrationTests {

    @Autowired
    CityRepository repository;

    // ...

}

	Tip
	The context loader guesses whether you want to test a web application or not (e.g. with MockMVC) by looking for the @WebIntegrationTest or @WebAppConfiguration annotations. (MockMVC and @WebAppConfiguration are part of spring-test).

If you want a web application to start up and listen on its normal port, so you can test it with HTTP (e.g. using RestTemplate), annotate your test class (or one of its superclasses) with @WebIntegrationTest. This can be very useful because it means you can test the full stack of your application, but also inject its components into the test class and use them to assert the internal state of the application after an HTTP interaction. For example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SampleDataJpaApplication.class)
@WebIntegrationTest
public class CityRepositoryIntegrationTests {

    @Autowired
    CityRepository repository;

    RestTemplate restTemplate = new TestRestTemplate();

    // ... interact with the running server

}

	Note
	Spring’s test framework will cache application contexts between tests. Therefore, as long as your tests share the same configuration, the time consuming process of starting and stopping the server will only happen once, regardless of the number of tests that actually run.

To change the port you can add environment properties to @WebIntegrationTest as colon- or equals-separated name-value pairs, e.g. @WebIntegrationTest("server.port:9000"). Additionally you can set the server.port and management.port properties to 0 in order to run your integration tests using random ports. For example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = MyApplication.class)
@WebIntegrationTest({"server.port=0", "management.port=0"})
public class SomeIntegrationTests {

    // ...

}

See Section 67.5, “Discover the HTTP port at runtime” for a description of how you can discover the actual port that was allocated for the duration of the tests.

39.3.1 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.

	Note
	The annotations described above can be used with Spock, i.e. you can annotate your Specification with @WebIntegrationTest to suit the needs of your tests.

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

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

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

import org.junit.Rule;
import org.junit.Test;
import org.springframework.boot.test.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"));
	}

}

public class MyTest {

	RestTemplate template = new TestRestTemplate();

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

}