JUnit 5 vs JUnit 4

JUnit 5 aims to adapt java 8 style of coding and to be more robust and flexible than JUnit 4. In this post, JUnit 5 vs JUnit 4, we will focus on some major differences between junit 4 and junit 5.

1. JUnit 5 vs JUnit 4 – Annotations

Most of annotations in both versions are same, but few differs. Here is a quick comparison.

2. Other differences between JUnit 5 and JUnit 4

2.1. Architecture

JUnit 4 has everything bundled into single jar file.

Junit 5 is composed of 3 sub-projects i.e. JUnit Platform, JUnit Jupiter and JUnit Vintage.

1. JUnit Platform

   It defines the TestEngine API for developing new testing frameworks that runs on the platform.

2. JUnit Jupiter

   It has all new junit annotations and TestEngine implementation to run tests written with these annotations.

3. JUnit Vintage

   To support running JUnit 3 and JUnit 4 written tests on the JUnit 5 platform.

2.2. Required JDK Version

Junit 4 requires Java 5 or higher.

Junit 5 requires Java 8 or higher.

2.3. Assertions

In Junit 4, org.junit.Assert has all assert methods to validate expected and resulted outcomes.
They accept extra parameter for error message as FIRST argument in method signature. e.g.

public static void assertEquals(long expected, long actual)
public static void assertEquals(String message, long expected, long actual)

In JUnit 5, org.junit.jupiter.Assertions contains most of assert methods including additional assertThrows() and assertAll() methods. assertAll() is in experimental state as of today, and is used for grouped assertions.
JUnit 5 assertions methods also have overloaded methods to support passing error message to be printed in case test fails e.g.

public static void assertEquals(long expected, long actual)
public static void assertEquals(long expected, long actual, String message)
public static void assertEquals(long expected, long actual, Supplier messageSupplier)

2.4. Assumptions

In Junit 4, org.junit.Assume contains methods for stating assumptions about the conditions in which a test is meaningful. It has following five methods:

1. assumeFalse()
2. assumeNoException()
3. assumeNotNull()
4. assumeThat()
5. assumeTrue()

In Junit 5, org.junit.jupiter.api.Assumptions contains methods for stating assumptions about the conditions in which a test is meaningful. It has following three methods:

1. assumeFalse()
2. assumingThat​()
3. assumeTrue()

2.5. Tagging and Filtering

In Junit 4, @category annotation is used.

In Junit 5, @tag annotation is used.

2.6. Test Suites

In Junit 4, @RunWith and @Suite annotation. e.g.

import org.junit.runner.RunWith;
import org.junit.runners.Suite;

@RunWith(Suite.class)
@Suite.SuiteClasses({
        ExceptionTest.class, 
        TimeoutTest.class
})
public class JUnit4Example 
{
}

In Junit 5, @RunWith, @SelectPackages and @SelectClasses e.g.

import org.junit.platform.runner.JUnitPlatform;
import org.junit.platform.suite.api.SelectPackages;
import org.junit.runner.RunWith;

@RunWith(JUnitPlatform.class)
@SelectPackages("com.howtodoinjava.junit5.examples")
public class JUnit5Example 
{
}

2.7. 3rd Party Integration

In Junit 4, there is no integration support for 3rd party plugins and IDEs. They have to rely on reflection.

JUnit 5 has dedicated sub-project for this purpose i.e. JUnit Platform. It defines the TestEngine API for developing a testing framework that runs on the platform.

Drop me your thoughts about this comparison between junit 5 and junit 4 in comments section.

Happy Learning !!