5-Dec

Get started with JUnit 5

JUnit 5 was released two years ago. Are you still running your tests with JUnit 4.12? Let’s change that, and get you started with JUnit 5.

3 min read

By John Ringø

December 5, 2019

Moving from 4.x to 5.x

If you want to use features available in Java 8 and above, you really should move to JUnit 5.

To migrate from JUnit 4.x to JUnit 5 you don’t have to rewrite all your tests at once. If you want to start using JUnit 5, do it. JUnit Vintage helps us with this. Get rid of JUnit 4 and include the JUnit Vintage Engine on your classpath. The vintage engine runs your old JUnit 4 tests in the context of JUnit 5.

Just add the following dependency to your pom.xml if you use Maven:

<dependency>
    <groupId>org.junit.vintage</groupId>
    <artifactId>junit-vintage-engine</artifactId>
    <version>${junit5.version}</version>
    <scope>test</scope>
</dependency>

So far, so good. You should now be able to run your old JUnit 4.x tests with JUnit 5, but you're still not able to write new tests with JUnit 5. Add the following dependencies to your pom.xml to be able to use the new features provided with JUnit 5 in your tests:

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-api</artifactId>
    <version>${junit5.version}</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>${junit5.version}</version>
    <scope>test</scope>
</dependency>

Now you should be ready to get started with JUnit 5. Start by converting some of your old test annotations to the ones provided with JUnit 5.

Basic annotations

I won’t go into detail about every annotation in JUnit 5, but I’d like to focus on a few of them. The most important annotation is of course @Test, which is still used to denote that a given method is a test method. However, in JUnit 5 the @Test-annotation doesn’t declare any attributes. Test expectations, like expected throwables, should now be handled in an assertion instead.

Some of the annotations that have changed from JUnit 4 to JUnit 5:

The @Before and @After annotations have changed to @BeforeEach and @AfterEach
@BeforeAll and @AfterAll have been renamed to @BeforeClass and @AfterClass
@Ignore no longer exists. You can use @Disabled instead. Or maybe you can use some of the included annotations for conditional execution? Is your test only supposed to work on a specific OS? @EnabledOnOs({ LINUX, MAC }). Or maybe it shouldn’t run on Java 9? @DisabledOnJre(JAVA_9)

Integrating your tests with other frameworks

In JUnit 4 you could specify different test runners to integrate your tests with other frameworks, like the Spring Framework with the @RunWith annotation.

@RunWith(SpringJUnit4ClassRunner.class)
public class MySpringTest {
    // All your Spring magic here
}

@RunWith no longer exists in JUnit 5. It has been replaced by @ExtendWith, which provides similar functionality.

@ExtendWith(SpringExtension.class)
public class MyOtherSpringTest {
    // Still your Spring magic here
}

You should have enough to get started with JUnit 5 in your projects. JUnit has an excellent JUnit 5 User Guide that you can use for a more comprehensive introduction to how you can best write your tests with JUnit 5.

If you want more handy JUnit 5 tips, be sure to check out:

Useful new features in JUnit 5

Up next...

Loading…

Proudly powered by