Setting Up JUnit with Spring Boot Test

Whether you are building REST APIs, service-layer logic, or data-access layers, Spring Boot offers first-class support for JUnit and provides convenient annotations and utilities for writing clean, maintainable tests.

1. Required Dependencies

Spring Boot uses JUnit Jupiter (JUnit 5/6 platform) out of the box.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>

testImplementation 'org.springframework.boot:spring-boot-starter-test'

This single dependency includes:

• JUnit Jupiter
• Spring Test
• Spring Boot Test
• Mockito
• AssertJ
• JSONAssert
• Hamcrest

2. Overriding JUnit Version

Spring Boot provides automatic support for managing the version of JUnit used in our project. If your build relies on dependency management support from Spring Boot, you should not import JUnit’s Bill of Materials (BOM) in your build script since that would result in duplicate (and potentially conflicting) management of JUnit dependencies.

If you need to override the version of a dependency used in your Spring Boot application, you have to override the exact name of the version property defined in the BOM used by the Spring Boot plugin.

<properties>
    <junit-jupiter.version>6.0.0</junit-jupiter.version>
</properties>

ext['junit-jupiter.version'] = '6.0.0'

3. Standard Spring Boot Test Folder Structure

Spring Boot automatically follows the given below folder structure because:

• Maven/Gradle convention locates test classes under src/test/java
• JUnit scans this folder during the test phase
• Spring Boot looks for application-test.properties under src/test/resources

project-root/
 ├── src/
 │    ├── main/
 │    │    ├── java/
 │    │    │    └── com/example/demo/...
 │    │    └── resources/
 │    │         └── application.properties
 │    └── test/
 │         ├── java/
 │         │    └── com/example/demo/...
 │         └── resources/
 │              └── application-test.properties
 ├── pom.xml or build.gradle

4. Conclusion

JUnit and Spring Boot Test provide a robust and scalable testing ecosystem. With almost zero setup, you gain:

• Full application context support
• Fast, isolated slices (Web, JPA, MVC)
• Out-of-the-box mocking
• Clean, expressive test style

Whether you are testing a single service, a complex REST API, or a JPA repository, Spring Boot’s integration with JUnit ensures that your tests remain simple, predictable, and maintainable.

Happy Learning!!