...

Below you have just a taste of some of the new features JUnit 5 has got to offer. Check out the user guide for a more complete list.

@DisplayName 
A display name can now be set for a test. This will be shown instead of the method name and will make output both easier to read and format. You can even include spaces and emojis.

@DisplayName("Single test successful")
@Test
void successTest() {
    log.info("Success");
}

Dynamic Tests
Dynamic on-the-fly tests can be made using @TestFactory and lambdas. These tests must return instances of Streams, Collections, Iterables, or Iterators of DynamicNode instances. These cases are executed lazily and so is generated at run-time.

...

@Test
void multipleAssertionsTest() {
    assertAll( 
  		() -> assertEquals(1, 2), 
  		() -> assertTrue(3 < 4), 
	);
}

Assumptions
These were already present in JUnit 4 but I thought they were worth a mention because in JUnit 5 they can also use Java 8 lambdas. According to the JUnit 5 user guide “Assumptions provide a basic form of dynamic behavior but are intentionally rather limited in their expressiveness”. They are useful because a failed Assumption does not fail a test,  it aborts it. This is useful if you only want to perform tests under certain conditions like on certain platforms or only if certain variables are present in the current runtime environment.

@Test
void testOnlyOnCertainMachines() {
   assumeTrue("dev".equals(System.getenv("ENV")),
   () -> "Aborting test as not needed on this computer");
   // rest of the test to run
}

ParameterizedTests
These allow you to run a test case multiple times with different arguments. These arguments can be strings, literal values, methods, Enums, CSV files, etc. @ParameterisedTest ultimately lets you avoid using unnecessary testing loops or duplicating test code.

@ParameterizedTest
@ValueSource(ints = { 1, 2, 3 })
void testWithValueSource(int argument) {
   assertTrue(argument > 0 && argument < 4);
}

Declarative Timeouts
@Timeout isn’t limited to being placed on test cases themselves. Along with the aforementioned test cases, @Timeout can also be placed at the type level, where it will provide a default timeout for all test cases declared in the class, this can be overridden by adding a @Timeout to a test case. @Timeout can also be added to lifecycle methods, @BeforeAll, @BeforeEach​, @AfterEach, @AfterAll​.

@Test
@Timeout(unit = TimeUnit.MILLISECONDS, value = 500L) // Default unit is seconds, but other options available
public void testTestCaseTimeout() throws InterruptedException {
	Thread.sleep(600);
}

Asserting exceptions

The @Testannotation no longer takes an expected argument. The Jupiter API provides a much tidier way of writing this type of test.

@Test
void exceptionThrownIfTryToSetAlertStatusToNull() {
  IllegalArgumentException actual = assertThrows(IllegalArgumentException.class,
                                                 () -> testee.setAlertStatus(null));
  assertEquals("Alert status cannot be set to null.", actual.getMessage());
}

Temporary Directory Extension

The built-in TempDirectory extension is used to create and clean up a temporary directory for an individual test or all tests in a test class. It is registered by default. To use it, annotate a non-private field of type java.nio.file.Path orjava.io.File with @TempDir or add a parameter of type java.nio.file.Path or java.io.File annotated with @TempDir to a lifecycle method or test method.

@Test
void writeItemsToFile(@TempDir Path tempDir) throws IOException {
    Path file = tempDir.resolve("test.txt");
    new ListWriter(file).write("a", "b", "c");
    assertEquals(singletonList("a,b,c"), Files.readAllLines(file));
}

Declarative Extension Registration

Developers can register one or more extensions declaratively by annotating a test interface, test class, test method, or custom composed annotation with @ExtendWith(…​) and supplying class references for the extensions to register.

...

//creating a custom extension
public class TimingExtension implements BeforeTestExecutionCallback, AfterTestExecutionCallback {
    private static final Logger logger = Logger.getLogger(TimingExtension.class.getName());
    private static final String START_TIME = "start time";

    @Override
    public void beforeTestExecution(ExtensionContext context) throws Exception {
        getStore(context).put(START_TIME, System.currentTimeMillis());
    }

    @Override
    public void afterTestExecution(ExtensionContext context) throws Exception {
        Method testMethod = context.getRequiredTestMethod();
        long startTime = getStore(context).remove(START_TIME, long.class);
        long duration = System.currentTimeMillis() - startTime;

        logger.info(() ->
            String.format("Method [%s] took %s ms.", testMethod.getName(), duration));
    }

    private Store getStore(ExtensionContext context) {
        return context.getStore(Namespace.create(getClass(), context.getRequiredTestMethod()));
    }
}

//using the custom extension
@ExtendWith(TimingExtension.class)
class TimingExtensionTests {

    @Test
    void sleep20ms() throws Exception {
        Thread.sleep(20);
    }

    @Test
    void sleep50ms() throws Exception {
        Thread.sleep(50);
    }
}

Parallel Test execution

By default, JUnit Jupiter tests are run sequentially in a single thread. Running tests in parallel — for example, to speed up execution — is available as an opt-in feature since version 5.3. To enable parallel execution, set thejunit.jupiter.execution.parallel.enabled configuration parameter to true — for example, in junit-platform.properties (see Configuration Parameters for other options). Please note that enabling this property is only the first step required to execute tests in parallel. If enabled, test classes and methods will still be executed sequentially by default. Whether or not a node in the test tree is executed concurrently is controlled by its execution mode. The following two modes are available.

  - SAME_THREAD: Force execution in the same thread used by the parent. For example, when used on a test method, the test method will be executed in the same thread as any @BeforeAll or @AfterAll methods of the containing test class.

 - CONCURRENT: Execute concurrently unless a resource lock forces execution in the same thread.

# Configuration parameters to execute top-level classes in parallel but methods in same thread
junit.jupiter.execution.parallel.enabled = true
junit.jupiter.execution.parallel.mode.default = same_thread
junit.jupiter.execution.parallel.mode.classes.default = concurrent
or
# Configuration parameters to execute top-level classes in sequentially but their methods in parallel
junit.jupiter.execution.parallel.enabled = true
junit.jupiter.execution.parallel.mode.default = concurrent
junit.jupiter.execution.parallel.mode.classes.default = same_thread
or
# Configuration parameters to execute top-level classes in parallel and their methods in parallel
junit.jupiter.execution.parallel.enabled = true
junit.jupiter.execution.parallel.mode.default = concurrent
junit.jupiter.execution.parallel.mode.classes.default = concurrent

Migration from JUnit 4

Although the JUnit Jupiter programming model and extension model will 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.

Maven dependencies

<dependencies>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-api</artifactId>
			<version>${junit.jupiter.version}</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-engine</artifactId>
			<version>${junit.jupiter.version}</version>
			<scope>test</scope>
		</dependency>
        <dependency> <!-- temporary until all junit4 tests have been migrated -->
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>${junit.version}</version>
			<scope>test</scope>
		</dependency>
		<dependency> <!-- temporary until all junit4 tests have been migrated -->
			<groupId>org.junit.vintage</groupId>
			<artifactId>junit-vintage-engine</artifactId>
			<version>${junit.vintage.version}</version>
			<scope>test</scope>
		</dependency>
	</dependencies>

...