# 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

# 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.");
	}
}

🛠️ Auto-refactor Available

You can auto refactor this with jSparrow.
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# Properties

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

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