[[migrating-from-junit4]] == Migrating from JUnit 4 Although the JUnit Jupiter programming model and extension model do not support JUnit 4 features such as `Rules` and `Runners` natively, it is not expected that source code maintainers will need to update all of their existing tests, test extensions, and custom build test infrastructure to migrate to JUnit Jupiter. Instead, JUnit provides a gentle migration path via a _JUnit Vintage test engine_ which allows existing tests based on JUnit 3 and JUnit 4 to be executed using the JUnit Platform infrastructure. Since all classes and annotations specific to JUnit Jupiter reside under the `org.junit.jupiter` base package, having both JUnit 4 and JUnit Jupiter in the classpath does not lead to any conflicts. It is therefore safe to maintain existing JUnit 4 tests alongside JUnit Jupiter tests. Furthermore, since the JUnit team will continue to provide maintenance and bug fix releases for the JUnit 4.x baseline, developers have plenty of time to migrate to JUnit Jupiter on their own schedule. [[migrating-from-junit4-running]] === Running JUnit 4 Tests on the JUnit Platform Make sure that the `junit-vintage-engine` artifact is in your test runtime path. In that case JUnit 3 and JUnit 4 tests will automatically be picked up by the JUnit Platform launcher. See the example projects in the {junit5-samples-repo}[`junit5-samples`] repository to find out how this is done with Gradle and Maven. [[migrating-from-junit4-categories-support]] ==== Categories Support For test classes or methods that are annotated with `@Category`, the _JUnit Vintage test engine_ exposes the category's fully qualified class name as a <> for the corresponding test class or test method. For example, if a test method is annotated with `@Category(Example.class)`, it will be tagged with `"com.acme.Example"`. Similar to the `Categories` runner in JUnit 4, this information can be used to filter the discovered tests before executing them (see <> for details). [[migrating-from-junit4-tips]] === Migration Tips The following are topics that you should be aware of when migrating existing JUnit 4 tests to JUnit Jupiter. * Annotations reside in the `org.junit.jupiter.api` package. * Assertions reside in `org.junit.jupiter.api.Assertions`. - Note that you may continue to use assertion methods from `org.junit.Assert` or any other assertion library such as {AssertJ}, {Hamcrest}, {Truth}, etc. * Assumptions reside in `org.junit.jupiter.api.Assumptions`. - Note that JUnit Jupiter 5.4 and later versions support methods from JUnit 4's `org.junit.Assume` class for assumptions. Specifically, JUnit Jupiter supports JUnit 4's `AssumptionViolatedException` to signal that a test should be aborted instead of marked as a failure. * `@Before` and `@After` no longer exist; use `@BeforeEach` and `@AfterEach` instead. * `@BeforeClass` and `@AfterClass` no longer exist; use `@BeforeAll` and `@AfterAll` instead. * `@Ignore` no longer exists: use `@Disabled` or one of the other built-in <> instead - See also <>. * `@Category` no longer exists; use `@Tag` instead. * `@RunWith` no longer exists; superseded by `@ExtendWith`. * `@Rule` and `@ClassRule` no longer exist; superseded by `@ExtendWith` and `@RegisterExtension`. - See also <>. * `@Test(expected = ...)` and the `ExpectedException` rule no longer exist; use `Assertions.assertThrows(...)` instead. - See <> if you still need to use `ExpectedException`. * Assertions and assumptions in JUnit Jupiter accept the failure message as their last argument instead of the first one. - See <> for details. [[migrating-from-junit4-rule-support]] === Limited JUnit 4 Rule Support As stated above, JUnit Jupiter does not and will not support JUnit 4 rules natively. The JUnit team realizes, however, that many organizations, especially large ones, are likely to have large JUnit 4 code bases that make use of custom rules. To serve these organizations and enable a gradual migration path the JUnit team has decided to support a selection of JUnit 4 rules verbatim within JUnit Jupiter. This support is based on adapters and is limited to those rules that are semantically compatible to the JUnit Jupiter extension model, i.e. those that do not completely change the overall execution flow of the test. The `junit-jupiter-migrationsupport` module from JUnit Jupiter currently supports the following three `Rule` types including subclasses of these types: * `org.junit.rules.ExternalResource` (including `org.junit.rules.TemporaryFolder`) * `org.junit.rules.Verifier` (including `org.junit.rules.ErrorCollector`) * `org.junit.rules.ExpectedException` As in JUnit 4, Rule-annotated fields as well as methods are supported. By using these class-level extensions on a test class such `Rule` implementations in legacy code bases can be _left unchanged_ including the JUnit 4 rule import statements. This limited form of `Rule` support can be switched on by the class-level annotation `{EnableRuleMigrationSupport}`. This annotation is a _composed annotation_ which enables all rule migration support extensions: `VerifierSupport`, `ExternalResourceSupport`, and `ExpectedExceptionSupport`. You may alternatively choose to annotate your test class with `@EnableJUnit4MigrationSupport` which registers migration support for rules _and_ JUnit 4's `@Ignore` annotation (see <>). However, if you intend to develop a new extension for JUnit Jupiter please use the new extension model of JUnit Jupiter instead of the rule-based model of JUnit 4. [[migrating-from-junit4-ignore-annotation-support]] === JUnit 4 @Ignore Support In order to provide a smooth migration path from JUnit 4 to JUnit Jupiter, the `junit-jupiter-migrationsupport` module provides support for JUnit 4's `@Ignore` annotation analogous to Jupiter's `{Disabled}` annotation. To use `@Ignore` with JUnit Jupiter based tests, configure a _test_ dependency on the `junit-jupiter-migrationsupport` module in your build and then annotate your test class with `@ExtendWith(IgnoreCondition.class)` or `{EnableJUnit4MigrationSupport}` (which automatically registers the `IgnoreCondition` along with <>). The `IgnoreCondition` is an `{ExecutionCondition}` that disables test classes or test methods that are annotated with `@Ignore`. [source,java,indent=0] ---- include::{testDir}/example/IgnoredTestsDemo.java[tags=user_guide] ---- [[migrating-from-junit4-failure-message-arguments]] === Failure Message Arguments The `Assumptions` and `Assertions` classes in JUnit Jupiter declare arguments in a different order than in JUnit 4. In JUnit 4 assertion and assumption methods accept the failure message as the first argument; whereas, in JUnit Jupiter assertion and assumption methods accept the failure message as the last argument. For instance, the method `assertEquals` in JUnit 4 is declared as `assertEquals(String message, Object expected, Object actual)`, but in JUnit Jupiter it is declared as `assertEquals(Object expected, Object actual, String message)`. The rationale for this is that a failure message is _optional_, and optional arguments should be declared after required arguments in a method signature. The methods affected by this change are the following: - Assertions * `assertTrue` * `assertFalse` * `assertNull` * `assertNotNull` * `assertEquals` * `assertNotEquals` * `assertArrayEquals` * `assertSame` * `assertNotSame` * `assertThrows` - Assumptions * `assumeTrue` * `assumeFalse`