Replace JUnit 4 Assertions with JUnit Jupiter

Description

This rule contributes to a stepwise transition to JUnit 5 by replacing the JUnit 4 assertion methods by the equivalent JUnit 5 ones. In JUnit 5, all methods used to carry out assertions are declared in org.junit.jupiter.api.Assertions (opens new window), while in JUnit 4 the equivalent assertion methods are declared in org.junit.Assert (opens new window).

This rule looks for invocations of overloaded methods of the JUnit 4 class Assert, and replaces them with the invocations of equivalent - also overloaded - assertion alternatives declared in the JUnit 5 class Assertions. See the following table for the equivalent assertions.

Assertions in Junit 4 org.junit.Assert	Assertions in JUnit 5 org.junit.jupiter.api.Assertions
Assert.assertArrayEquals (opens new window)	Assertions.assertArrayEquals (opens new window)
Assert.assertEquals (opens new window)	Assertions.assertEquals (opens new window)
Assert.assertFalse (opens new window)	Assertions.assertFalse (opens new window)
Assert.assertNotEquals (opens new window)	Assertions.assertNotEquals (opens new window)
Assert.assertNotNull (opens new window)	Assertions.assertNotNull (opens new window)
Assert.assertNotSame (opens new window)	Assertions.assertNotSame (opens new window)
Assert.assertNull (opens new window)	Assertions.assertNull (opens new window)
Assert.assertSame (opens new window)	Assertions.assertSame (opens new window)
Assert.assertTrue (opens new window)	Assertions.assertTrue (opens new window)
Assert.fail (opens new window)	Assertions.fail (opens new window)

By replacing each of these JUnit 4 Assert methods by the corresponding Jupiter alternatives, this rule promotes a stepwise transition to JUnit 5.

Requirements

This rule requires the following library to be present:

• junit:junit:4.13
• org.junit.jupiter:junit-jupiter-api:5.4.0

Benefits

Migrates JUnit 4 tests to JUnit 5.

Tags

Tags

Java 8, Testing, JUnit

Code Changes

Replacing Imports

Pre

import static org.junit.Assert.assertEquals;

import org.junit.jupiter.api.Test;

public class TestExample {
	@Test
	void test() {
		assertEquals(0L, 0L);
	}
}

Post

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

import org.junit.jupiter.api.Test;

public class TestExample {
	@Test
	void test() {
		assertEquals(0L, 0L);
	}
}

Replacing Invocations with a Message

Pre

import static org.junit.Assert.assertEquals;

import org.junit.jupiter.api.Test;

public class TestExample {
	@Test
	void test() {
		assertEquals("Expecting that 0L equals 0L.", 0L, 0L);
	}
}

Post

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

import org.junit.jupiter.api.Test;

public class TestExample {
	@Test
	void test() {
		assertEquals(0L, 0L, "Expecting that 0L equals 0L.");
	}
}

Replacing the Assert Qualifier

Pre

import static org.assertmethods.AssertMethods.assertEquals;

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

public class TestExample {
	@Test
	void test() {
		Assert.assertEquals(0L, 0L);
		assertEquals(0L, 0L);
	}
}

Post

import static org.assertmethods.AssertMethods.assertEquals;

import org.junit.Assert;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

public class TestExample {
	@Test
	void test() {
		Assertions.assertEquals(0L, 0L);
		assertEquals(0L, 0L);
	}
}

Replacing ThrowingRunnable by Executable

Pre

import static org.junit.Assert.assertThrows;

import java.io.IOException;

import org.junit.function.ThrowingRunnable;
import org.junit.jupiter.api.Test;

public class ChangingTypeOfThrowingRunnable {
	@Test
	public void testExpectedIOException() {
		ThrowingRunnable runnable = () -> throwsIOException("Simply throw an IOException");
		assertThrows("Test changing type of ThrowingRunnable variable.", IOException.class, runnable);
	}
}

Post

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

import java.io.IOException;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.function.Executable;

public class ChangingTypeOfThrowingRunnable {
	@Test
	public void testExpectedIOException() {
		Executable runnable = () -> throwsIOException("Simply throw an IOException");
		assertThrows(IOException.class, runnable, "Test changing type of ThrowingRunnable variable.");
	}
}

Use a Java Refactoring Tool

No license required

You can review this refactoring on your code without a license by installing jSparrow to your Eclipse IDE. Install the plug-in from Eclipse IDE: Eclipse Marketplace.

System-wide Refactoring

Do you want to automate this refactoring (and many more) to your system-wide code? The automatic application of this system-wide refactoring can be unlocked by acquiring your jSparrow license.

Properties

Property	Value
Rule ID	ReplaceJUnit4AssertionsWithJupiter
First seen in jSparrow version	3.28.0
Minimum Java version	8
Remediation cost	2 min