JUnit 5 Tutorial

This JUnit 5 tutorial talks about how it adapted java 8 style of coding and several other features as well. Learn how it’s different from JUnit 3 or 4.

JUnit 5 is most widely used testing framework for java applications. For very long time, JUnit has been doing its job perfectly. In between, JDK 8 brought very exciting features in java and most notably lambda expressions. JUnit 5 aims to adapt java 8 style of coding and several other features as well, that’s why java 8 is required to create and execute tests in JUnit 5 (though it is possible to execute tests written with JUnit 3 or JUnit 4 for backward compatibility).

Table of Contents

Architecture
Installation
Annotations
Writing Tests
Test Suites
Assertions
Assumptions
Backward Compatibility
Conclusion

JUnit 5 Architecture

As compared to JUnit 4, JUnit 5 is composed of several different modules from three different sub-projects:

JUnit 5 = JUnit Platform + JUnit Jupiter + JUnit Vintage

1. JUnit Platform

   To be able to launch junit tests, IDEs, build tools or plugins need to include and extend platform APIs. It defines the TestEngine API for developing new testing frameworks that runs on the platform.
   It also provides a Console Launcher to launch the platform from the command line and build plugins for Gradle and Maven.

2. JUnit Jupiter

   It includes new programming and extension models for writing tests. It has all new junit annotations and TestEngine implementation to run tests written with these annotations.

3. JUnit Vintage

   It primary purpose is to support running JUnit 3 and JUnit 4 written tests on the JUnit 5 platform. It’s there are backward compatibility.

Installation

You can use JUnit 5 in your maven or gradle project by including minimum two dependencies i.e. Jupiter Engine Dependency and Platform Runner Dependency.

//pom.xml

<dependency>
	<groupId>org.junit.jupiter</groupId>
	<artifactId>junit-jupiter-engine</artifactId>
	<version>${junit.jupiter.version}</version>
</dependency>
<dependency>
	<groupId>org.junit.platform</groupId>
	<artifactId>junit-platform-runner</artifactId>
	<version>${junit.platform.version}</version>
	<scope>test</scope>
</dependency>

//build.gradle

testRuntime("org.junit.jupiter:junit-jupiter-engine:5.0.0-M4")
testRuntime("org.junit.platform:junit-platform-runner:1.0.0-M4")

Official build.gradle and pom.xml are good references, in case of any doubt.

Read More: Maven Example | Gradle Example

JUnit 5 Annotations

JUnit 5 offers following annotations to write tests.

Writing Tests in JUnit 5

There is not much changed between JUnit 4 and JUnit 5 in test writing styles. Here is sample tests with their life cycle methods.

import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;

import com.howtodoinjava.junit5.examples.Calculator;

public class AppTest {
	
	@BeforeAll
	static void setup(){
		System.out.println("@BeforeAll executed");
	}
	
	@BeforeEach
	void setupThis(){
		System.out.println("@BeforeEach executed");
	}
	
	@Tag("DEV")
	@Test
    void testCalcOne() 
	{
		System.out.println("======TEST ONE EXECUTED=======");
		Assertions.assertEquals( 4 , Calculator.add(2, 2));
    }
	
	@Tag("PROD")
	@Disabled
	@Test
    void testCalcTwo() 
	{
		System.out.println("======TEST TWO EXECUTED=======");
		Assertions.assertEquals( 6 , Calculator.add(2, 4));
    }
	
	@AfterEach
	void tearThis(){
		System.out.println("@AfterEach executed");
	}
	
	@AfterAll
	static void tear(){
		System.out.println("@AfterAll executed");
	}
}

Test Suites

Using JUnit 5 test suites, you can run tests spread into multiple test classes and different packages. JUnit 5 provides two annotations: @SelectPackages and @SelectClasses to create test suites.

To execute the suite, you will use @RunWith(JUnitPlatform.class).

@RunWith(JUnitPlatform.class)
@SelectPackages("com.howtodoinjava.junit5.examples")
public class JUnit5TestSuiteExample 
{
}

Additionally, you can use following annotations for filtering test packages, classes or even test methods.

1. @IncludePackages and @ExcludePackages to filter packages
2. @IncludeClassNamePatterns and @ExcludeClassNamePatterns to filter test classes
3. @IncludeTags and @ExcludeTags to filter test methods

@RunWith(JUnitPlatform.class)
@SelectPackages("com.howtodoinjava.junit5.examples")
@IncludePackages("com.howtodoinjava.junit5.examples.packageC")
@ExcludeTags("PROD")
public class JUnit5TestSuiteExample 
{
}

Read More : JUnit 5 Test Suites

Assertions

Assertions help in validating the expected output with actual output of a testcase. To keep things simple, all JUnit Jupiter assertions are static methods in the org.junit.jupiter.Assertions class e.g. assertEquals(), assertNotEquals().

void testCase() 
{
    //Test will pass
    Assertions.assertNotEquals(3, Calculator.add(2, 2));
     
    //Test will fail 
    Assertions.assertNotEquals(4, Calculator.add(2, 2), "Calculator.add(2, 2) test failed");
     
    //Test will fail 
    Supplier<String> messageSupplier  = ()-> "Calculator.add(2, 2) test failed";
    Assertions.assertNotEquals(4, Calculator.add(2, 2), messageSupplier);
}

Read More: JUnit 5 Assertions

Assumptions

Assumptions class provides static methods to support conditional test execution based on assumptions. A failed assumption results in a test being aborted. Assumptions are typically used whenever it does not make sense to continue execution of a given test method. In test report, these test will be marked as passed.

JUnit jupiter Assumptions class has two such methods: assumeFalse(), assumeTrue().

public class AppTest {
    @Test
    void testOnDev() 
    {
        System.setProperty("ENV", "DEV");
        Assumptions.assumeTrue("DEV".equals(System.getProperty("ENV")), AppTest::message);
    }
     
    @Test
    void testOnProd() 
    {
        System.setProperty("ENV", "PROD");
        Assumptions.assumeFalse("DEV".equals(System.getProperty("ENV")));  
    }
     
    private static String message () {
        return "TEST Execution Failed :: ";
    }
}

Read More: JUnit 5 Assumptions

Backward Compatibility for JUnit 3 or JUnit 4

JUnit 4 has been here for a quite long time and there are numerous tests written in junit 4. JUnit Jupiter need to support those tests as well. For this purpose, JUnit Vintage sub-project is developed.

JUnit Vintage provides a TestEngine implementation for running JUnit 3 and JUnit 4 based tests on the JUnit 5 platform.

Conclusion

JUnit 5 is still in development. It seems so exciting and feature rich. And now its open for extension by third party tools and APIs. As a test writer, you may not feel that much different but when you will go for its extension or try to develop any IDE plugin, you will praise it.

As a developer, you may also consider adding test templates into eclipse IDE to improve your development speed.

Write your thoughts about this JUnit 5 tutorial in comments.

Happy Learning !!