JUnit 6 Tutorial with Examples

JUnit is the de-facto standard testing framework for Java (and the JVM), widely used for writing automated unit tests. With the release of JUnit 6, the framework has matured further into a modern, unified platform.

Under the hood, JUnit 6 combines:

• the JUnit Platform (test launch infrastructure),
• JUnit Jupiter (the programming and extension model for writing new tests),
• and (optionally) JUnit Vintage (for running legacy JUnit 3 / JUnit 4 tests).

JUnit 6.0.1 = JUnit Platform + JUnit Jupiter + JUnit Vintage

1. JUnit 5 vs JUnit 6

The following table showing the main differences between JUnit 6 and JUnit 5, along with examples wherever helpful.

2. Maven and Gradle

If you are using Maven, here is a minimal pom.xml snippet to set up JUnit 6 for testing.

<project>
  ...
  <properties>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
  </properties>

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.junit</groupId>
        <artifactId>junit-bom</artifactId>
        <version>6.0.0</version>  <!-- or latest JUnit 6 version -->
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

  <dependencies>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>3.0.0</version> <!-- minimum required for JUnit 6 -->
      </plugin>
    </plugins>
  </build>
  ...
</project>

In case of Gradle, use the following configuration:

Requires Gradle 7.3+ because of the Java 17 baseline.

plugins {
    id 'java'
}

repositories {
    mavenCentral()
}

dependencies {
    testImplementation(platform("org.junit:junit-bom:6.0.0"))

    testImplementation("org.junit.jupiter:junit-jupiter")
    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
}

test {
    useJUnitPlatform()
}

3. A JUnit 6 Simple Test

Here’s a minimal example to get started with JUnit 6. This class runs the tests and assets few basic assumptions.

package com.howtodoinjava;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.DisplayName;

import static org.junit.jupiter.api.Assertions.*;

public class AppTest {

  @Test
  @DisplayName("Simple test to verify that 1 + 1 equals 2")
  void testAddition() {

    assertEquals(2, 1 + 1);
  }

  @Test
  @DisplayName("Test string equality")
  void testStringEquality() {

    String expected = "Hello World!";
    String actual = "Hello World!";
    assertEquals(expected, actual);
  }

  @Test
  @DisplayName("Test boolean assertion")
  void testBooleanAssertion() {

    assertTrue(true);
    assertFalse(false);
  }

  @Test
  @DisplayName("Test not null assertion")
  void testNotNull() {

    App app = new App();
    assertNotNull(app);
  }
}

4. Conclusion

JUnit 6 is a modern, polished evolution of JUnit 5 that embraces Java 17+, improves extension handling, enhances performance, and adds new features like nullability annotations and native Kotlin coroutine support. Writing tests remains simple and familiar, using the same @Test annotation and clear assertion APIs.

Happy Learning !!