As mentioned in JUnit5 documentation, it is possible to integrate JUnit4 with JUnit5:

____
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 a new org.junit.jupiter base package, having both JUnit 4 and JUnit Jupiter in the classpath does not lead to any conflicts.

____
However, maintaining both systems is a temporary solution. This rule flags all the annotations from JUnit4 which would need to be migrated to JUnit5, hence helping migration of a project.


Here is the list of JUnit4 annotations tracked by the rule, with their corresponding annotations in JUnit5:

||JUnit4||JUnit5||

|``++org.junit.Test++``|``++org.junit.jupiter.api.Test++``|

|``++org.junit.Before++``|``++org.junit.jupiter.api.BeforeEach++``|

|``++org.junit.After++``|``++org.junit.jupiter.api.AfterEach++``|

|``++org.junit.BeforeClass++``|``++org.junit.jupiter.api.BeforeAll++``|

|``++org.junit.AfterClass++``|``++org.junit.jupiter.api.AfterAll++``|

|``++org.junit.Ignore++``|``++org.junit.jupiter.api.Disabled++``|


Note that the following annotations might requires some rework of the tests to have JUnit5 equivalent behavior. A simple replacement of the annotation won't work immediately:

||JUnit4||JUnit5||

|``++org.junit.experimental.categories.Category++``|``++org.junit.jupiter.api.Tag++``|

|``++org.junit.Rule++``|``++org.junit.jupiter.api.extension.ExtendWith++``|

|``++org.junit.ClassRule++``|``++org.junit.jupiter.api.extension.RegisterExtension++``|

|``++org.junit.runner.RunWith++``|``++org.junit.jupiter.api.extension.ExtendWith++``|


== Noncompliant Code Example

----
package org.foo;

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Ignore;
import org.junit.Test;
import org.junit.experimental.categories.Category;
import org.junit.runner.RunWith;

@RunWith(MyJUnit4Runner.class)
public class MyJUnit4Test {

  @BeforeClass
  public static void beforeAll() {
    System.out.println("beforeAll");
  }

  @AfterClass
  public static void afterAll() {
    System.out.println("AfterAll");
  }

  @Before
  public void beforeEach() {
    System.out.println("beforeEach");
  }

  @After
  public void afterEach() {
    System.out.println("afterEach");
  }

  @Test
  public void test1() throws Exception {
    System.out.println("test1");
  }

  public interface SomeTests { /* category marker */ }

  @Test
  @Category(SomeTests.class)
  public void test2() throws Exception {
    System.out.println("test2");
  }

  @Test
  @Ignore("Requires fix of #42")
  public void ignored() throws Exception {
    System.out.println("ignored");
  }
}
----


== Compliant Solution

----
package org.foo;

import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;

@ExtendWith(MyJUnit5Extension.class)
class MyJUnit5Test {

  @BeforeAll
  static void beforeAll() {
    System.out.println("beforeAll");
  }

  @AfterAll
  static void afterAll() {
    System.out.println("afterAll");
  }

  @BeforeEach
  void beforeEach() {
    System.out.println("beforeEach");
  }

  @AfterEach
  void afterEach() {
    System.out.println("afterEach");
  }

  @Test
  void test1() {
    System.out.println("test1");
  }

  @Test
  @Tag("SomeTests")
  void test2() {
    System.out.println("test2");
  }

  @Test
  @Disabled("Requires fix of #42")
  void disabled() {
    System.out.println("ignored");
  }
}
----


== See

* https://junit.org/junit5/docs/current/user-guide/#migrating-from-junit4[JUnit 5: Migrating from JUnit4]


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