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JUnit

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JUnit is a unit testing framework for the Java programming language. JUnit has been important in the development of test-driven development, and is one of a family of unit testing frameworks which is collectively known as xUnit that originated with SUnit.

JUnit is linked as a JAR at compile-time; the framework resides under package junit.framework for JUnit 3.8 and earlier, and under package org.junit for JUnit 4 and later.

A research survey performed in 2013 across 10,000 Java projects hosted on GitHub found that JUnit in a tie with slf4j-api, was the most commonly included external library. Each library was used by 30.7% of projects.

Example of JUnit test fixture

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A JUnit test fixture is a Java object. With older versions of JUnit, fixtures had to inherit from junit.framework.TestCase, but the new tests using JUnit 4 should not do this. Test methods must be annotated by the @Test annotation. If the situation requires it, it is also possible to define a method to execute before or after each or all of the test methods with the @Before or @After and @BeforeClass or @AfterClass annotations.

import org.junit.*;
public class FoobarTest {
    @BeforeClass
    public static void setUpClass throws Exception {
        // Code executed before the first test method
    }
    @Before
    public void setUp throws Exception {
        // Code executed before each test
    }
 
    @Test
    public void testOneThing {
        // Code that tests one thing
    }
    @Test
    public void testAnotherThing {
        // Code that tests another thing
    }
    @Test
    public void testSomethingElse {
        // Code that tests something else
    }
    @After
    public void tearDown throws Exception {
        // Code executed after each test 
    }
 
    @AfterClass
    public static void tearDownClass throws Exception {
        // Code executed after the last test method 
    }
}

Ports

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JUnit alternatives have been written in other languages including: