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

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5 NEWS FROM JUNIT 5 FROM REVOLUTION TO CONTINUOUS EVOLUTION

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5 MARC PHILIPP So ware Engineer at JUnit commi er since 2012 team lead since 2016 Twi er: Web: @marcphilipp marcphilipp.de

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5 ✋ SHOW OF HANDS

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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

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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?

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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

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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?

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5 BASICS (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190319‑javaland

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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

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5 KOTLIN SUPPORT 5.1 import org.junit.jupiter.api.* class KotlinAssertionsDemo { @Test fun `expected exception testing`() { val exception = assertThrows { Calculator().divide(1, 0) } assertEquals("/ by zero", exception.message) } @Test fun `grouped assertions`() { assertAll("Person properties", { assertEquals("Jane", person.firstName) }, { assertEquals("Doe", person.lastName) } ) } }

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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) {/*...*/} }

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5 MORE WAYS TO TEST (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190319‑javaland

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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

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5 PARALLEL EXECUTION 5.3 (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190319‑javaland

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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

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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, changes execu on mode to SAME_THREAD by default Extensible: implement MethodOrderer

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5 EXTENSIONS (DEMO) h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190319‑javaland

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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 Built‑in @TempDir support 5.4 User Guide

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5 COMPOSED ANNOTATIONS Use Jupiter annota ons as meta‑annota ons to create your own annota ons. @Retention(RUNTIME) @Target(METHOD) @ExtendWith(ConferenceExecutionCondition.class) @Tag("example") public @interface DisabledOnConference {}

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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") @EnabledIf / @DisabledIf("Math.random() < 0.5") (experimental)

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5 EXTENSION POINTS Lifecycle: BeforeAllCallback , BeforeEachCallback , BeforeTestExecutionCallback , TestExecutionExceptionHandler , AfterTestExecutionCallback , AfterEachCallback , AfterAllCallback Other: ExecutionCondition , TestInstanceFactory 5.3 , TestInstancePostProcessor , ParameterResolver , TestWatcher 5.4 , TestTemplateInvocationContextProvider

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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

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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?

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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

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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)

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5 COUPLING

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5 If JUnit is a pla orm, let’s design for it!

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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)

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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

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5 JUNIT 5 = JUPITER + VINTAGE + PLATFORM

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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

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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)

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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)

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5 THIRD‑PARTY ENGINES Specsy, Spek, KotlinTest, Cucumber, Drools, jqwik, Brahms, Mainrunner, … h ps:/ /github.com/junit‑team/junit5/wiki/Third‑party‑ Extensions

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5 USING MULTIPLE ENGINES (DEMO) h ps:/ /github.com/junit‑team/junit5‑ samples/tree/master/junit5‑mul ple‑engines

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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)

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5 TAG EXPRESSIONS 5.1 Precisely specify which tests to run based on tags: test { useJUnitPlatform { includeTags("(smoke & feature-a) | (!smoke & feature-b)") } }

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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

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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?

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5 ROADMAP AND ROADMAP AND ROADMAP AND ROADMAP AND ROADMAP AND RESOURCES RESOURCES RESOURCES RESOURCES RESOURCES Image: NASA

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5 IMPORTANT FUTURE MILESTONES Execu ng tests in user‑deﬁned threads/containers Global Timeouts New repor ng format that supports new features Declara ve Test Suites Parameterized Test Classes Scenario Tests Your ideas?

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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/

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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

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5 SUPPORT JUNIT Support the JUnit team with dona ons: h ps:/ /junit.org/sponsoring

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5 EXAMPLE CODE Jupiter: Pla orm: h ps:/ /github.com/marcphilipp/junit5‑ demo/tree/20190319‑javaland h ps:/ /github.com/junit‑team/junit5‑ samples/tree/master/junit5‑mul ple‑engines

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5 QUESTIONS? Come talk to Chris an Stein ( ) and me at the booth a er this talk or ping / on Twi er @sormuras @marcphilipp @juni eam

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5 THANKS!