2.10. Test Instance Lifecycle

In order to allow individual test methods to be executed in isolation and to avoid unexpected side effects due to mutable test instance state, JUnit creates a new instance of each test class before executing each test method (see Test Classes and Methods). This “per-method” test instance lifecycle is the default behavior in JUnit Jupiter and is analogous to all previous versions of JUnit.

If you would prefer that JUnit Jupiter execute all test methods on the same test instance, annotate your test class with @TestInstance(Lifecycle.PER_CLASS). When using this mode, a new test instance will be created once per test class. Thus, if your test methods rely on state stored in instance variables, you may need to reset that state in @BeforeEach or @AfterEach methods.

The “per-class” mode has some additional benefits over the default “per-method” mode. Specifically, with the “per-class” mode it becomes possible to declare @BeforeAll and @AfterAll on non-static methods as well as on interface default methods. The “per-class” mode therefore also makes it possible to use @BeforeAll and @AfterAll methods in @Nested test classes.

If you are authoring tests using the Kotlin programming language, you may also find it easier to implement @BeforeAll and @AfterAll methods by switching to the “per-class” test instance lifecycle mode.

2.10.1. Changing the Default Test Instance Lifecycle

If a test class or test interface is not annotated with @TestInstance, JUnit Jupiter will use a default lifecycle mode. The standard default mode is PER_METHOD; however, it is possible to change the default for the execution of an entire test plan. To change the default test instance lifecycle mode, set the junit.jupiter.testinstance.lifecycle.default configuration parameter to the name of an enum constant defined in TestInstance.Lifecycle, ignoring case. This can be supplied as a JVM system property, as a configuration parameter in the LauncherDiscoveryRequest that is passed to the Launcher, or via the JUnit Platform configuration file (see Configuration Parameters for details).

For example, to set the default test instance lifecycle mode to Lifecycle.PER_CLASS, you can start your JVM with the following system property.

-Djunit.jupiter.testinstance.lifecycle.default=per_class

Note, however, that setting the default test instance lifecycle mode via the JUnit Platform configuration file is a more robust solution since the configuration file can be checked into a version control system along with your project and can therefore be used within IDEs and your build software.

To set the default test instance lifecycle mode to Lifecycle.PER_CLASS via the JUnit Platform configuration file, create a file named junit-platform.properties in the root of the class path (e.g., src/test/resources) with the following content.

junit.jupiter.testinstance.lifecycle.default = per_class