This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Boot 4.1.0!

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")
	}

}

OutputCaptureExtension

OutputCaptureExtension 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")
	}

}