Test Utilities

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

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:

Java
Kotlin

import org.springframework.boot.test.context.ConfigDataApplicationContextInitializer;
import org.springframework.test.context.ContextConfiguration;

@ContextConfiguration(classes = Config.class, initializers = ConfigDataApplicationContextInitializer.class)
class MyConfigFileTests {

	// ...

}

import org.springframework.boot.test.context.ConfigDataApplicationContextInitializer
import org.springframework.test.context.ContextConfiguration

@ContextConfiguration(classes = [Config::class], initializers = [ConfigDataApplicationContextInitializer::class])
class MyConfigFileTests {

	// ...

}

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.

TestPropertyValues

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

Java
Kotlin

import org.junit.jupiter.api.Test;

import org.springframework.boot.test.util.TestPropertyValues;
import org.springframework.mock.env.MockEnvironment;

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

class MyEnvironmentTests {

	@Test
	void testPropertySources() {
		MockEnvironment environment = new MockEnvironment();
		TestPropertyValues.of("org=Spring", "name=Boot").applyTo(environment);
		assertThat(environment.getProperty("name")).isEqualTo("Boot");
	}

}

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test
import org.springframework.boot.test.util.TestPropertyValues
import org.springframework.mock.env.MockEnvironment

class MyEnvironmentTests {

	@Test
	fun testPropertySources() {
		val environment = MockEnvironment()
		TestPropertyValues.of("org=Spring", "name=Boot").applyTo(environment)
		assertThat(environment.getProperty("name")).isEqualTo("Boot")
	}

}

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:

Java
Kotlin

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;

import org.springframework.boot.test.system.CapturedOutput;
import org.springframework.boot.test.system.OutputCaptureExtension;

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

@ExtendWith(OutputCaptureExtension.class)
class MyOutputCaptureTests {

	@Test
	void testName(CapturedOutput output) {
		System.out.println("Hello World!");
		assertThat(output).contains("World");
	}

}

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.extension.ExtendWith
import org.springframework.boot.test.system.CapturedOutput
import org.springframework.boot.test.system.OutputCaptureExtension

@ExtendWith(OutputCaptureExtension::class)
class MyOutputCaptureTests {

	@Test
	fun testName(output: CapturedOutput?) {
		println("Hello World!")
		assertThat(output).contains("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 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.

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

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:

Java
Kotlin

import org.junit.jupiter.api.Test;

import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.http.ResponseEntity;

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

class MyTests {

	private final TestRestTemplate template = new TestRestTemplate();

	@Test
	void testRequest() {
		ResponseEntity<String> headers = this.template.getForEntity("https://myhost.example.com/example", String.class);
		assertThat(headers.getHeaders().getLocation()).hasHost("other.example.com");
	}

}

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test
import org.springframework.boot.test.web.client.TestRestTemplate

class MyTests {

	private val template = TestRestTemplate()

	@Test
	fun testRequest() {
		val headers = template.getForEntity("https://myhost.example.com/example", String::class.java)
		assertThat(headers.headers.location).hasHost("other.example.com")
	}

}

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

Java
Kotlin

import java.time.Duration;

import org.junit.jupiter.api.Test;

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.context.TestConfiguration;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.http.HttpHeaders;

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

@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class MySpringBootTests {

	@Autowired
	private TestRestTemplate template;

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

	@TestConfiguration(proxyBeanMethods = false)
	static class RestTemplateBuilderConfiguration {

		@Bean
		RestTemplateBuilder restTemplateBuilder() {
			return new RestTemplateBuilder().setConnectTimeout(Duration.ofSeconds(1))
				.setReadTimeout(Duration.ofSeconds(1));
		}

	}

}

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test
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.context.TestConfiguration
import org.springframework.boot.test.web.client.TestRestTemplate
import org.springframework.boot.web.client.RestTemplateBuilder
import org.springframework.context.annotation.Bean
import java.time.Duration

@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class MySpringBootTests(@Autowired val template: TestRestTemplate) {

	@Test
	fun testRequest() {
		val headers = template.getForEntity("/example", String::class.java).headers
		assertThat(headers.location).hasHost("other.example.com")
	}

	@TestConfiguration(proxyBeanMethods = false)
	internal class RestTemplateBuilderConfiguration {

		@Bean
		fun restTemplateBuilder(): RestTemplateBuilder {
			return RestTemplateBuilder().setConnectTimeout(Duration.ofSeconds(1))
				.setReadTimeout(Duration.ofSeconds(1))
		}

	}

}