This session will give you an overview of the latest and greatest in the world of testing using JUnit Jupiter (a.k.a. JUnit 5) and the Spring Framework. The focus will be major new features in JUnit Jupiter 5.8 and 5.9 as well as recent and upcoming enhancements to Spring's integration testing support.

1. Sam Brannen
@sam_brannen
Spring I/O 2022
Testing with
and
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JUnit

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3. Sam Brannen
● Staff Software Engineer
● Java Developer for over 20 years
● Spring Framework Core Committer since 2007
● JUnit 5 Core Committer since October 2015

4. Cover w/ Image
Agenda
● JUnit 5.8
● JUnit 5.9
● Spring 5.3
● Spring 6.0
● Q&A

5. JUnit Jupiter Support in Spring
JUnit Jupiter and Spring are a great match for testing
● Spring Framework
● @ExtendWith(SpringExtension.class)
● @SpringJUnitConfig
● @SpringJUnitWebConfig
● Spring Boot
● @SpringBootTest
● @WebMvcTest, etc.

6. JUnit 5.8

7. Major Features in JUnit Platform 1.8
● Declarative test suites via @Suite classes
● SuiteTestEngine in junit-platform-suite-engine module
● new annotations in junit-platform-suite-api module
■ @Suite, @ConfigurationParameter, @SelectUris, @SelectFile, etc.
● UniqueIdTrackingListener
○ TestExecutionListener that tracks the unique IDs of all tests
○ generates a file containing the unique IDs
○ can be used to rerun those tests
■ for example, with GraalVM Native Build Tools

8. Example: Suites before 5.8 – Now Deprecated
// Uses JUnit 4 to run JUnit 5
@RunWith(JUnitPlatform.class)
@SuiteDisplayName("Integration Tests")
@IncludeEngines("junit-jupiter")
@SelectPackages("com.example")
@IncludeTags("integration-test")
public class IntegrationTestSuite {
}

9. Example: Suites with JUnit 5.8
// Uses JUnit 5 to run JUnit 5
@Suite
@SuiteDisplayName("Integration Tests")
@IncludeEngines("junit-jupiter")
@SelectPackages("com.example")
@IncludeTags("integration-test")
public class IntegrationTestSuite {
}

10. Small Enhancements in JUnit 5.8
https://junit.org/junit5/docs/5.8.0/release-notes/
● More fine-grained Java Flight Recorder (JFR) events
● plus support on Java 8 update 262 or higher
● assertThrowsExactly()
○ alternative to assertThrows()
● assertInstanceOf()
○ instead of assertTrue(obj instanceof X)
● @RegisterExtension fields may now be private

11. New in JUnit Jupiter 5.8

12. Test Class Execution Order
● ClassOrderer API analogous to the MethodOrderer API
○ ClassName
○ DisplayName
○ OrderAnnotation
○ Random
● Global configuration via junit.jupiter.testclass.order.default configuration
parameter for all test classes
● for example, to optimize the build
● Local configuration via @TestClassOrder for @Nested test classes

13. Example: @TestClassOrder
@TestClassOrder(ClassOrderer.OrderAnnotation.class)
class OrderedNestedTests {
@Nested
@Order(1)
class PrimaryTests {
@Test
void test1() {}
}
@Nested
@Order(2)
class SecondaryTests {
@Test
void test2() {}
}
}

14. @TempDir – New Behavior
Due to popular demand from the community…
● @TempDir previously created a single temporary directory per context
● @TempDir can now be used to create multiple temporary directories
● JUnit now creates a separate temporary directory per @TempDir annotation
● Revert to the old behavior by setting the junit.jupiter.tempdir.scope
configuration parameter to per_context

15. @ExtendWith on Fields and Parameters
Improves programming model
● @RegisterExtension: register extensions via fields programmatically
○ nothing new
● @ExtendWith: can now register extensions via fields and parameters declaratively
● fields: static or instance
● parameters: constructor, lifecycle method, test method
● typically as a meta-annotation
● avoids the need to declare @ExtendWith at the class or method level

16. Example: RandomNumberExtension
@Target({ ElementType.FIELD, ElementType.PARAMETER })
@Retention(RetentionPolicy.RUNTIME)
@ExtendWith(RandomNumberExtension.class)
public @interface Random {
}
class RandomNumberExtension implements BeforeAllCallback,
BeforeEachCallback, ParameterResolver {
// implementation...
}

17. Example: @Random in Action
class RandomNumberTests {
@Random
private int randomNumber1;
RandomNumberTests(@Random int randomNumber2) {
}
@BeforeEach
void beforeEach(@Random int randomNumber3) {
}
@Test
void test(@Random int randomNumber4) {
}
}

18. Named API
● Named: container that associates a name with a given payload
○ The meaning of the payload depends on the context
○ Named.of() vs. Named.named()
● DynamicTests.stream() can consume Named input and will use each name-value pair
as the display name and value for each generated dynamic test
● In parameterized tests using @MethodSource or @ArgumentSource, arguments can
now have explicit names supplied via the Named API
○ explicit name used in display name instead of the argument value

19. Example: Named Dynamic Tests
@TestFactory
Stream<DynamicTest> dynamicTests() {
Stream<Named<String>> inputStream = Stream.of(
named("racecar is a palindrome", "racecar"),
named("radar is also a palindrome", "radar"),
named("mom also seems to be a palindrome", "mom"),
named("dad is yet another palindrome", "dad")
);
return DynamicTest.stream(inputStream,
text -> assertTrue(isPalindrome(text)));
}

20. AutoCloseable Arguments in Parameterized Tests
● In parameterized tests, arguments that implement AutoCloseable will now be
automatically closed after the test completes
● Allows for automatic cleanup of resources
○ closing a file
○ stopping a server
○ etc.
● Similar to the CloseableResource support in the ExtensionContext.Store

21. Small Enhancements in JUnit Jupiter 5.8.x
https://junit.org/junit5/docs/5.8.2/release-notes/
● Support for text blocks in @CsvSource
● CSV headers in display names for @CsvSource and @CsvFileSource
● Custom quote character support in @CsvSource and @CsvFileSource
● Java 18 support in the JRE enum
● Access to the ExecutionMode in the ExtensionContext

22. Example: @CsvSource Before Text Blocks
@ParameterizedTest
@CsvSource({
"apple, 1",
"banana, 2",
"'lemon, lime', 0xF1",
"strawberry, 700_000"
})
void testWithCsvSource(String fruit, int rank) {
assertNotNull(fruit);
assertNotEquals(0, rank);
}

23. Example: @CsvSource with Text Blocks
@ParameterizedTest
@CsvSource(quoteCharacter = '"', textBlock = """
# FRUIT, RANK
apple, 1
banana, 2
"lemon, lime", 0xF1
strawberry, 700_000
""")
void testWithCsvSource(String fruit, int rank) {
assertNotNull(fruit);
assertNotEquals(0, rank);
}

24. Example: @CsvSource with CSV Headers
@ParameterizedTest(name = "[{index}] {arguments}")
@CsvSource(useHeadersInDisplayName = true, textBlock = """
FRUIT, RANK
apple, 1
banana, 2
'lemon, lime', 0xF1
strawberry, 700_000
""")
void testWithCsvSource(String fruit, int rank) {
assertNotNull(fruit);
assertNotEquals(0, rank);
}

25. JUnit 5.9

26. JUnit Platform 1.9 M1
https://junit.org/junit5/docs/5.9.0-M1/release-notes/
● XML reports in new Open Test Reporting format
○ https://github.com/ota4j-team/open-test-reporting
● New IterationSelector
○ for selecting a subset of a test’s or container’s iterations
● Various improvements to ConsoleLauncher
○ --single-color and --color-palette
○ --list-engines
○ JUnit Platform Suite Engine included in stand-alone JAR

27. JUnit Jupiter 5.9 M1
● Configurable cleanup mode for @TempDir
○ ALWAYS, ON_SUCCESS, NEVER
● New TestInstancePreConstructCallback extension API
○ counterpart to existing TestInstancePreDestroyCallback
● Reusable parameter resolution for custom extension methods via
ExecutableInvoker API
○ accessed via ExtensionContext
○ @BeforeTransaction / @AfterTransaction in Spring?
● @MethodSource factory methods can accept arguments
○ resolved by ParameterResolver extensions

28. DEMO
@MethodSource and Spring

29. Spring Framework 5.3

30. New in Spring Framework 5.3.x (1/2)
https://github.com/spring-projects/spring-framework/releases
● Test configuration is now discovered on enclosing classes for @Nested test classes
● ApplicationEvents abstraction for capturing application events published in the
ApplicationContext during a test
● Set spring.test.constructor.autowire.mode in junit-platform.properties
● Detection for @Autowired violations in JUnit Jupiter
● Improvements for file uploads and multipart support in MockMvc and
MockRestServiceServer
● Various enhancements in MockHttpServletRequest and MockHttpServletResponse

31. New in Spring Framework 5.3.x (2/2)
● Improved SQL script parsing regarding delimiters and comments
● ExceptionCollector testing utility
● Soft assertions for MockMvc and WebTestClient
● Support for HtmlFileInput.setData() with HtmlUnit and MockMvc
● setDefaultCharacterEncoding() in MockHttpServletResponse
● Default character encoding for responses in MockMvc

32. Tip: Use Text Blocks... Where you can
● @Sql(statements = …)
○ Just works
● Maybe other places in Spring as well
● Maybe in other frameworks

33. Example: @Nested tests before 5.3
@SpringJUnitConfig(TestConfig.class)
@ActiveProfiles("dev")
@Transactional
class DevTests {
@Nested
@SpringJUnitConfig(TestConfig.class)
@ActiveProfiles("dev")
@Transactional
class OrderTests { /* tests */ }
@Nested
@SpringJUnitConfig(PricingConfig.class)
class PricingTests { /* tests */ }
}

34. Example: @Nested tests after 5.3
@SpringJUnitConfig(TestConfig.class)
@ActiveProfiles("dev")
@Transactional
class DevTests {
@Nested
class OrderTests { /* tests */ }
@Nested
@NestedTestConfiguration(OVERRIDE)
@SpringJUnitConfig(PricingConfig.class)
class PricingTests { /* tests */ }
}

35. Example: ApplicationEvents
@SpringJUnitConfig(/* ... */)
@RecordApplicationEvents
class OrderServiceTests {
@Autowired OrderService orderService;
@Autowired ApplicationEvents events;
@Test
void submitOrder() {
// Invoke method in OrderService that publishes an event
orderService.submitOrder(new Order(/* ... */));
// Verify that 1 OrderSubmitted event was published
assertThat(events.stream(OrderSubmitted.class)).hasSize(1);
}
}

36. Example: MockMvc without Soft Assertions
mockMvc.perform(get("/person/5").accept(APPLICATION_JSON))
.andExpect(status().isOk())
.andExpect(jsonPath("$.name").value("Jane"));

37. Example: MockMvc with Soft Assertions
mockMvc.perform(get("/person/5").accept(APPLICATION_JSON))
.andExpectAll(
status().isOk(),
jsonPath("$.name").value("Jane")
);

38. Example: WebTestClient without Soft Assertions
webTestClient.get().uri("/test").exchange()
.expectStatus().isOk()
.expectBody(String.class).isEqualTo("hello");

39. Example: WebTestClient with Soft Assertions
webTestClient.get().uri("/test").exchange()
.expectAll(
spec -> spec.expectStatus().isOk(),
spec -> spec.expectBody(String.class).isEqualTo("hello")
);

40. Example: MockMvc default response character encoding
MockMvc mockMvc;
@BeforeEach
void setup(WebApplicationContext wac) {
this.mockMvc = webAppContextSetup(wac)
.defaultResponseCharacterEncoding(StandardCharsets.UTF_8)
.build();
}
@Test
void getPerson() throws Exception {
this.mockMvc.perform(get("/person/1").characterEncoding(UTF_8))
.andExpect(status().isOk())
.andExpect(content().encoding(UTF_8));
}

41. Spring Framework 6.0

42. Testing Enhancements in Spring 6.0
● Module path scanning support
○ for example, when using Maven Surefire and patched modules
○ https://github.com/sbrannen/spring-module-system
● Mechanism for avoiding repeated attempts to load a failing ApplicationContext
○ likely with configurable number of retries
● Accept arguments in @BeforeTransaction and @AfterTransaction methods
● Otherwise, not much else currently planned for 6.0 GA
○ rather for 6.0.x

43. Q&A

44. Thank you
Twitter: @sam_brannen
© 2022 Spring. A VMware-backed project.
and JUnit