Motivation

New useful functionality will be added:

1. Check to throw exceptions:

public void shouldRaiseAnException () throws Exception {
    Assertions.assertThrows(Exception.class, () -> {
            //...
    });
}

In JUnit4:

@Test(expected = Exception.class)

2. Ability to check timeouts:

@Test(timeout = 1)
public void shouldFailBecauseTimeout () throws InterruptedException {
    Thread.sleep(10);
}

@Test
public void shouldFailBecauseTimeout () throws InterruptedException {
    Assertions.assertTimeout(Duration.ofMillis(1), () -> Thread.sleep(10));
}

3. Compatibility with Java8, it is possible to write lambdas directly from Assert:

@Test
public void shouldFailBecauseTheNumbersAreNotEqual_lazyEvaluation () {
    Assertions.assertTrue(
        2 == 3,
        () -> "Numbers " + 2 + " and " + 3 + " are not equal!");
}


@Test
public void shouldAssertAllTheGroup () {
    List<Integer> list = Arrays.asList(1, 2, 4);
    Assertions.assertAll("List is not incremental",
        () -> Assertions.assertEquals(list.get(0).intValue(), 1),
        () -> Assertions.assertEquals(list.get(1).intValue(), 2),
        () -> Assertions.assertEquals(list.get(2).intValue(), 3));
}

4. Assumption. Tests will be executed under conditions:

@Test
public void whenEnvironmentIsWeb_thenUrlsShouldStartWithHttp () {
    assumingThat("WEB".equals(System.getenv("ENV")),
        () -> {
            assertTrue("http".startsWith(address));
        });
}

5. Useful to check flaky tests:

@RepeatedTest(value = 3, name = "Custom name {currentRepetition}/{totalRepetitions}")
void repeatedTestWithCustomDisplayName (TestInfo testInfo){
    assertEquals(2, Math.addExact(1, 1), "1 + 1 should equal 2");
}

6. Parameterized Test:

@ParameterizedTest
@ValueSource(strings = {"Hello", "JUnit"})
void withValueSource (String word){
    assertNotNull(word);
}

7. Migration from JUnit 4 to 5 is not so difficult, as backward compatibility is available.

Description

1. Migrate examples-module.
   1. Add dependencies to parent/pom.xml
   2. Change adding suites to IgniteExamplesSelfTestSuite
   3. Launch IgniteExamplesMLTestSuite separately under JUnit4, because it is impossible to override JUnitPlatform constructor as well as Suite constructor
   4. Change annotations and imports in test classes
   5. Ignore commented tests
2. Migrate core module in the same way as examples. Classes with dynamic tests do not need to be changed. This is due to the fact that in JUnit5 it is not possible to launch static and dynamic tests under one surefire version. 
   Positive side: the dynamic tests amount is not so big, they locate in specific places. The all JUnit5 opportunity can not be used in dynamic tests (@TestFactory).
   According to the previous points, the next should be added:
   1. Remove test timeouts and add timeouts via annotations
   2. Replace exception checking according to JUnit5 style
   3. Replace some tests on parameterized where it is necessary (the same tests are used with different parameters)
3. Migrate modules where JUnit tests exist. Check list:
   1. aop
   2. aws
   3. camel
   4. cassandra
   5. clients
   6. cloud
   7. comatibility
   8. compress
   9. direct-io
   10. flink
   11. flume
   12. gce
   13. geospastial
   14. hadoop
   15. hibernate 4.2, 5.1, 5.3, core
   16. ignored
   17. indexing
   18. jcl
   19. jta
   20. kafka
   21. kubernates
   22. log4j
   23. log4j2
   24. ml
   25. mqtt
   26. osgi
   27. rest-htpp
   28. rocketmql
   29. schedule
   30. slf4j
   31. spark
   32. spring, spring-data, 2.0
   33. ssh
   34. storm
   35. tensorflow
   36. twitter
   37. urldeploy
   38. web-console
   39. yarn
   40. zeromq
   41. zookeeper

Completion criteria for each point:

1. Tests can be launched under JUnit5. Usage of JUnit 5 annotations becomes available, for example, @RepeatedTest
2. There are no additional fails on TeamCity.

Completion criteria on the whole:

1. All modules satisfy the previous two criteria
2. The community is informed about the migration to 5 and benefits of the newest version.

* Additional improvements to JUnit 3->4 migration.

1. Remove JUnit3TestLegacyAssertclass. Replace inheritance to imports
2. In JUnit3TestLegacySupport:
   
   1. Replace tearDown, setUp by @BeforeEach, @AfterEach annotations, where it is necessary
   2. The same situation with beforeTest, afterTest methods
   3. Replace beforeTestsStarted, afterTestsStopped by @BeforeAll, @AfterAll
   4. The rest methods move to GridAbstractTest.

Risks and Assumptions

• Additional fails on TC because of migration issues
• Performance degradation of tests execution.
  

Discussion Links

Devlist discussion.

Reference Links

Question to JUnit develop team about surefire version.

Tickets