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Unit Testing Java Applications using JUnit 5

Difference between JUnit 4 and JUnit 5

Explore the key distinctions between JUnit 4 and JUnit 5, focusing on annotation changes, test lifecycle hooks, and Java Development Kit compatibility. This lesson prepares you to migrate your unit tests to JUnit 5 with clarity on updated features and support.

We'll cover the following...

This lesson will help us understand the differences between JUnit 4 and JUnit 5.

JUnit 4 and JUnit 5 comparison

The table below shows a side-by-side comparison of annotations used in JUnit 4 and JUnit 5.

JUnit 5

JUnit 4

@Test

@Test

@BeforeEach

@Before

@BeforeAll

@BeforeClass

@AfterEach

@After

@AfterAll

@AfterClass

@Disabled

@Ignore

@Tag

@Category

@ExtendWith

@RunWith

Code example using JUnit 4

Below is a unit test code written in JUnit 4.

JUnit5 (Java 1.8)
package io.educative.junit5;
import org.junit.*;
public class HelloWorldTest {
    private Calculator calculator = new Calculator();
    @BeforeClass
    public static void setupClass() {
        System.out.println("Inside @BeforeClass method");
    }
    @AfterClass
    public static void tearDownClass() {
        System.out.println("Inside @AfterClass method");
    }
    @Before
    public void setup() {
        System.out.println("Inside @Before method");
    }
    @After
    public void tearDown() {
        System.out.println("Inside @After method");
    }
    @Test
    public void testAddition() {
        int result = calculator.add(1, 2);
        Assert.assertEquals(3, result);
    }
    @Test
    @Ignore
    public void testDivison() {
        int result = calculator.divide(2, 1);
        Assert.assertEquals(2, result);
    }
}
  • We define the test with the @Test annotation from the package org.junit.
  • We use the @BeforeClass, @Before, @After, and @AfterClass are used to hook into the life cycle of the JUnit 4 tests.
  • We use the @Ignore annotation to skip the execution of a given test.

Code example using JUnit 5

Below is a unit test code written in JUnit 5.

JUnit5 (Java 1.8)
package io.educative.junit5;
import org.junit.jupiter.api.*;
public class HelloWorldTest {
    private Calculator calculator = new Calculator();
    @BeforeAll
    static void setupClass() {
        System.out.println("Inside @BeforeAll method");
    }
    @AfterAll
    static void tearDownClass() {
        System.out.println("Inside @AfterAll method");
    }
    @BeforeEach
    void setup() {
        System.out.println("Inside @BeforeEach method");
    }
    @AfterEach
    void tearDown() {
        System.out.println("Inside @AfterEach method");
    }
    @Test
    public void testAddition() {
        int result = calculator.add(1, 2);
        Assertions.assertEquals(3, result);
    }
    @Test
    @Disabled
    public void testDivison() {
        int result = calculator.divide(2, 1);
        Assertions.assertEquals(2, result);
    }
}
  • We define the test with the @Test annotation from the org.junit.jupiter.api package.
  • We use @BeforeAll, @BeforeEach, @AfterEach, and @AfterAll to hook into the life cycle of the JUnit5 tests.
  • The @Disabled annotation is used to skip the execution of a given test.

Java Development Kit (JDK) compatibility

The main difference to keep in mind before migrating to JUnit 5 is the JDK Compatibility.

JUnit 4 supports JDK 5 and later versions. JUnit 5 supports JDK 8 and later versions.