News from JUnit 5.x: From Revolution to Continuous Evolution

2017 marked a revolutionary year for the most popular Java testing framework: after two years of development, JUnit 5 was finally released – the first major release in over a decade. But work hasn’t stopped since then. If anything, the amount of feedback and the number of feature requests from the community have increased considerably. As a consequence, there have been 4 new 5.x releases with additional features and enhancements, and the JUnit team is committed to keeping up the pace and shipping a new 5.x release every few months. So it’s fair to say that JUnit is back to evolutionary releases, but the team intends to deliver them far more frequently than in the past.

In this session, we’ll take a closer look at the new features such as improved Kotlin support, module path scanning, programmatic extension registration, tag expressions, annotation-based conditional test execution, improved parameterized tests and, last but not least, parallel test execution. Moreover, we’ll see how the most popular Java build systems (Maven, Gradle, Ant) now provide built-in first-class support for running tests on the JUnit Platform. To round off the session, we will look at the roadmap of what’s still to come.

Transcript

1. 5 NEWS FROM JUNIT 5 FROM REVOLUTION TO CONTINUOUS EVOLUTION
2. 5 MARC PHILIPP So ware Engineer at JUnit commi er since 2012 team lead since 2016 Twi er: Web: @marcphilipp marcphilipp.de
3. 5 ✋ SHOW OF HANDS
4. 5 JUNIT 5 RELEASES 5.0 – September 10, 2017 5.1 – February 18, 2018 5.2 – April 29, 2018 5.3 – September 11, 2018 5.4 – February 7, 2019
5. 5 AGENDA 1. How to write tests and extensions using JUnit 5? 2. What is the JUnit Pla orm and why do we need it? 3. What’s s ll to come and how to get started?
6. 5 JUNIT JUPITER JUNIT JUPITER JUNIT JUPITER JUNIT JUPITER JUNIT JUPITER THE NEW TESTING FRAMEWORK FOR JAVA THE NEW TESTING FRAMEWORK FOR JAVA THE NEW TESTING FRAMEWORK FOR JAVA THE NEW TESTING FRAMEWORK FOR JAVA THE NEW TESTING FRAMEWORK FOR JAVA Image: NASA
7. 5 JUPITER? Nope, it’s just a new name so we can easily dis nguish it from the old JUnit and the other parts of JUnit 5. … and it’s the fi h planet from the sun. Is wri ng tests rocket science now?
8. 5 BASICS (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190427‑jeeconf
9. 5 BASICS (RECAP) @Test is s ll a thing, but in org.junit.jupiter.api @Disabled instead of @Ignore @BeforeAll , @BeforeEach , @AfterEach , @AfterAll have new names Assertions look similar – a few new ones like assertThrows , assertAll Custom @DisplayNames to ease camel‑case fa gue @TestInstance(PER_METHOD or PER_CLASS) @Tag instead of @Category
10. 5 DISPLAY NAME GENERATORS 5.4 @DisplayNameGeneration(ReplaceUnderscores.class) class A_year_is_not_supported { @Test void if_it_is_zero() {/*...*/} @ParameterizedTest @ValueSource(ints = { -1, -4 }) void if_it_is_negative(int year) {/*...*/} }
11. 5 TEST METHOD ORDERING 5.4 @TestMethodOrder(Random.class) to ensure tests don’t rely on any order @TestMethodOrder(Alphanumeric.class) and @TestMethodOrder(OrderAnnotation.class) for integra on tests Extensible: implement MethodOrderer
12. 5 KOTLIN SUPPORT 5.1 import org.junit.jupiter.api.* class KotlinAssertionsDemo { @Test fun `expected exception testing`() { val exception = assertThrows<ArithmeticException> { Calculator().divide(1, 0) } assertEquals("/ by zero", exception.message) } @Test fun `grouped assertions`() { assertAll("Person properties", { assertEquals("Jane", person.firstName) }, { assertEquals("Doe", person.lastName) } ) } }
13. 5 MORE WAYS TO TEST (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190427‑jeeconf
14. 5 MORE WAYS TO TEST (RECAP) @ParameterizedTest with different @Source annota ons @ValueSource , @EnumSource , @CsvSource , @CsvFileSource , @MethodSource , @NullSource 5.4 , @EmptySource 5.4 , @ArgumentsSource(MyProvider.class) , @YourCustomSource @RepeatedTest for flaky tests @TestFactory to produce dynamic tests
15. 5 PARALLEL EXECUTION 5.3 (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190427‑jeeconf
16. 5 PARALLEL EXECUTION 5.3 (RECAP) Tests are run sequen ally by default Opt‑in and configure parallel execu on via configura on parameters @Execution(SAME_THREAD or CONCURRENT) Use @ResourceLock as declara ve synchroniza on mechanism
17. 5 EXTENSIONS (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190427‑jeeconf
18. 5 EXTENSIONS (RECAP) Registra on (as many as you need): Declara ve: @ExtendWith on classes or methods Programma c: @RegisterExtension on fields 5.1 Global: Via ServiceLoader (see ) Implementa on: Extension marker interface one extension – n extension points/interfaces User Guide
19. 5 COMPOSED ANNOTATIONS Use Jupiter annota ons as meta‑annota ons to create your own annota ons. @Retention(RUNTIME) @Target(METHOD) @ExtendWith(DisabledOnWeekdaysExtension.class) @Tag("example") public @interface DisabledOnWeekdays { DayOfWeek[] value(); }
20. 5 EXTENSION POINTS Lifecycle: BeforeAllCallback , BeforeEachCallback , BeforeTestExecutionCallback , TestExecutionExceptionHandler , AfterTestExecutionCallback , AfterEachCallback , AfterAllCallback Other: ExecutionCondition , ParameterResolver , TestInstanceFactory 5.3 , TestInstancePostProcessor , TestWatcher 5.4 , TestTemplateInvocationContextProvider
21. 5 BUILT‑IN TEMP DIR SUPPORT 5.4 import org.junit.jupiter.api.io.TempDir; @Test void writeAndReadFile(@TempDir Path tempDir) throws Exception { Path testFile = tempDir.resolve("test.txt"); Files.write(testFile, asList("foo", "bar")); List<String> actualLines = Files.readAllLines(testFile); assertIterableEquals(asList("foo", "bar"), actualLines); }
22. 5 BUILT‑IN CONDITIONS 5.1 @EnabledOnOs / @DisabledOnOs({LINUX, MAC, …}) @EnabledOnJre / @DisabledOnJre({JAVA_11, …}) @Enabled / DisabledIfSystemProperty(named = "someKey", matches = "someValue") @Enabled / DisabledIfEnvironmentVariable(named = "SOME_KEY", matches = "SOME_VALUE")
23. 5 THIRD‑PARTY EXTENSIONS JUnit Pioneer, Spring, Mockito, Testcontainers, Docker, Wiremock, JPA, Selenium/WebDriver, DbUnit, Ka a, Jersey, GreenMail, S3Mock, Citrus Framework, XWiki, … h ps:/ /github.com/junit‑team/junit5/wiki/Third‑party‑ Extensions
24. 5 AGENDA 1. How to write tests and extensions using JUnit 5? ✅ 2. What is the JUnit Pla orm and why do we need it? 3. What’s s ll to come and how to get started?
25. 5 JUNIT PLATFORM JUNIT PLATFORM JUNIT PLATFORM JUNIT PLATFORM JUNIT PLATFORM PLATFORM FOR TESTING ON THE JVM PLATFORM FOR TESTING ON THE JVM PLATFORM FOR TESTING ON THE JVM PLATFORM FOR TESTING ON THE JVM PLATFORM FOR TESTING ON THE JVM Image: NASA
26. 5 JUNIT AS A PLATFORM? JUnit has always been a pla orm for IDEs and build tools for other tes ng frameworks Closely coupled (internal APIs, reflec on, serializa on)
27. 5 COUPLING
28. 5 If JUnit is a pla orm, let’s design for it!
29. 5 SEPARATION OF CONCERNS 1. An API to write tests and extensions (Jupiter API) 2. Extensible mechanisms to discover and execute tests (Test Engine SPI) 3. An API for test execu on by tools (Launcher API)
30. 5 DESIGN GOALS Flexibility: Adding new features should be easy. It should be clear whether a change might poten ally break a client. Backward Compa bility: Test wri en with JUnit 3 and 4 should s ll run Forward Compa bility: Old IDEs and build tools should be able to execute new tests
32. 5 JUNIT 5 = JUPITER + VINTAGE + PLATFORM
33. 5 COMPATIBILITY / MIGRATION Vintage Engine to run JUnit 3/4 tests on the Pla orm @Category(UI.class) maps to com.acme.UI tag Limited support for JUnit 4 Rules to ease migra on Migra on support for @Ignore 5.4 IDEs provide tools to convert test classes to Jupiter API Community‑provided migra on tool: h ps:/ /github.com/boyarsky/convert‑junit4‑to‑junit5
34. 5 BUILD TOOL SUPPORT Na ve support in Gradle (≥ 4.6), Ant (≥ 1.10.3), and Maven Surefire (≥ 2.22.0) ConsoleLauncher to run tests from the command line or to support other build tools (e.g. Bazel)
35. 5 IDE SUPPORT Excellent support IntelliJ IDEA (≥ 2016.2) Eclipse (≥ 4.7.1a) Visual Studio Code (Java Test Runner ≥ 0.4.0) Netbeans (≥ 10.0) For other tools, there’s @RunWith(JUnitPlatform)
36. 5 THIRD‑PARTY ENGINES Specsy, Spek, KotlinTest, Cucumber, Drools, jqwik, Brahms, Mainrunner, … h ps:/ /github.com/junit‑team/junit5/wiki/Third‑party‑ Extensions
37. 5 USING MULTIPLE ENGINES (DEMO) h ps:/ /github.com/marcphilipp/junit5‑pla orm‑demo
38. 5 USING MULTIPLE ENGINES (RECAP) Mul ple test engines can be used in a single test run Dis nc on between testImplementation and testRuntimeOnly dependencies Allows to gradually migrate tests from one test engine to another (e.g. from Vintage to Jupiter)
39. 5 TAG EXPRESSIONS 5.1 Precisely specify which tests to run based on tags: test { useJUnitPlatform { includeTags("(smoke & feature-a) | (!smoke & feature-b)") } }
40. 5 SUPPORT FOR JAVA MODULES 5.1 Execute all tests in a module: Scan the module path: $ java -jar junit-platform-console-standalone-1.4.0.jar \ --select-module com.acme.foo $ java -jar junit-platform-console-standalone-1.4.0.jar \ --scan-modules
41. 5 AGENDA 1. How to write tests and extensions using JUnit 5? ✅ 2. What is the JUnit Pla orm and why do we need it? ✅ 3. What’s s ll to come and how to get started?
42. 5 ROADMAP AND ROADMAP AND ROADMAP AND ROADMAP AND ROADMAP AND RESOURCES RESOURCES RESOURCES RESOURCES RESOURCES Image: NASA
43. 5 IMPORTANT FUTURE MILESTONES Reusable test discovery for test engines 5.5 M1 Execu ng tests in user‑defined threads 5.5 M2 Declara ve/global meouts 5.5 M2 New repor ng format that supports new features (e.g. tags, display names, report entries) Declara ve Test Suites Parameterized Test Classes Your ideas?
44. 5 GETTING STARTED User Guide: Sample projects for Ant, Bazel, Gradle, and Maven: Javadoc: h p:/ /junit.org/junit5/docs/current/user‑guide/ h ps:/ /github.com/junit‑team/junit5‑samples h p:/ /junit.org/junit5/docs/current/api/
45. 5 WANTED: FEEDBACK! StackOverflow: Code & Issues: Chat with the team: Twi er: h p:/ /stackoverflow.com/ques ons/tagged/junit5 h ps:/ /github.com/junit‑team/junit5/ h ps:/ /gi er.im/junit‑team/junit5 h ps:/ /twi er.com/juni eam
46. 5 SUPPORT JUNIT Support the JUnit team with dona ons: h ps:/ /junit.org/sponsoring
47. 5 EXAMPLE CODE Jupiter: Pla orm: h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190427‑jeeconf h ps:/ /github.com/marcphilipp/junit5‑pla orm‑demo
48. 5 QUESTIONS? / on Twi er @marcphilipp @juni eam
49. 5 ДЯКУЮ!