JUnit 5 @ Solutions HH

1. JUnit 5
2. Christian Stein • Software developer @ MICROMATA Kassel/Bonn • JUnit 5 core team member since 2017 • Github: https://github.com/sormuras • Twitter: @sormuras
3. Marc Philipp • Staff Software Engineer @ in Karlsruhe • JUnit Maintainer since 2012 • Twitter: @marcphilipp • Web: http://www.marcphilipp.de
4. Programming Model
5. DEMO https://github.com/marcphilipp/junit5-demo/tree/20170906-solutions.hamburg
6. Meta Annotations Annotations can be combined to enable re-use:
 
 @Target(ElementType.METHOD)
 @Retention(RetentionPolicy.RUNTIME)
 @Tag("integration")
 @Test
 public @interface IntegrationTest {} Usage:
 
 @IntegrationTest
 void test() {}
 Equivalent:
 
 @Tag("integration")
 @Test
 void test() {}
7. @ParameterizedTest Sources • @ValueSource(ints = { 1, 2, 3 }) • @EnumSource(TimeUnit.class) • @MethodSource(names = "myProviderMethod") • @CsvSource({ "foo, 1", "bar, 2", "'baz, qux', 3" }) • @CsvFileSource(resources = "/two-column.csv") • @ArgumentsSource(MyArgumentsProvider.class) • @YourCustomSource
8. @Nested Tests @DisplayName("A stack") class TestingAStackDemo { @Test @DisplayName("is instantiated with new Stack()") void isInstantiatedWithNew() {/* ... */} @Nested @DisplayName("when new") class WhenNew { @BeforeEach void createNewStack() {/* ... */} @Test @DisplayName("is empty") void isEmpty() {/* ... */} // ... @Nested @DisplayName("after pushing an element") class AfterPushing { @BeforeEach void pushAnElement() {/* ... */} @Test @DisplayName("it is no longer empty") void isNotEmpty() {/* ... */} // ... } } }
9. Dynamic Tests @TestFactory Stream<DynamicTest> dynamicTestsFromStream() { return IntStream.iterate(0, n -> n + 2).limit(100) .mapToObj(n -> dynamicTest("test" + n, () -> { assertTrue(n % 2 == 0); })); }
10. @RepeatedTest @RepeatedTest(10) void repeatedTest() { // ... }
11. Why do we need a new JUnit?
12. Runner • Very powerful: Almost every aspect of test execution can be changed • But: You can only have one Runner per test class! • You can’t combine Runners, e.g.
 SpringJUnit4ClassRunner + Parameterized
13. Rules • Extension mechanism introduced in JUnit 4.7 • Wraps execution of a test (@Rule) or a test class (@ClassRule) • Designed to be combined — great for simple use cases • But: a single rule cannot be used for method-level and class-level callbacks, no support for instance-level callbacks
14. http://blog.takipi.com/the-top-100-java-libraries-in-2016-after-analyzing-47251-dependencies/
15. Existing Architecture Everyone uses the junit.jar.
16. Renaming a private field should not break anything, right? 4.11 4.12-beta-1
17. –Johannes Link, https://jaxenter.com/crowdfunding-for-junit-lambda-is- underway-119546.html „The success of JUnit as a platform prevents the development of JUnit as a tool.“
18. Design Goals for JUnit 5 • Modern programming model for writing tests (Java 8!) • Powerful extension model with a focus on composability • API Segregation: Decouple test execution/reporting from test definition • Compatibility with older releases + migration path • Modularization + no external dependencies
19. Modularization
20. Separation of Concerns 1. An API to write tests (Jupiter API) 2. Extensible mechanisms to discover and execute tests (Test Engine SPI) 3. An API for test execution by tools (Launcher API)
21. P L AT F O R M J U P I T E R V I N TA G E P A R T Y T H I R D
22. P L AT F O R M J U P I T E R V I N TA G E P A R T Y T H I R D
23. JUnitPlatform Runner for a single class import org.junit.jupiter.api.Test; @RunWith(JUnitPlatform.class) public class JupiterTest { @Test void someTest() { // test something } }
24. JUnitPlatform Runner in suite mode @RunWith(JUnitPlatform.class) @SelectPackages("com.acme") @IncludeEngines({"junit-jupiter", "junit-vintage"}) public class JUnit4SuiteDemo { // this class can be run using JUnit 4 }
25. IDE Support • IntelliJ supports JUnit 5 ≥ M2 since 2016.2 • Eclipse support is available on Eclipse Marketplace:
 https://marketplace.eclipse.org/content/junit-5-support- beta-oxygen
 Will be integrated without requiring any additional work in Oxygen.1a • Interim solution for other IDEs: JUnitPlatform Runner
26. Build Tool Support • Gradle/Maven: Plugin/Provider available • see https://github.com/junit-team/junit5- samples • Manually: ConsoleLauncher
27. Compatibility • Backward compatibility (junit-vintage-engine) enables gradual migration of tests to Jupiter API • Forward compatibility (JUnitPlatform Runner) allows test execution with “old” tools
28. Extensions
29. Extension Registration • Declarative: Annotate your test classes or methods with @ExtendWith to register extensions • Supports an arbitrary number of extensions at the same time • May be used as a meta-annotation • Global: Opt-in support for registration via ServiceLoader
30. DEMO https://github.com/marcphilipp/junit5-demo/tree/20170906-solutions.hamburg
31. Extension Points • Conditional Test Execution • ExecutionCondition • General Purpose • TestInstancePostProcessor • ParameterResolver • TestTemplateInvocationContext- Provider • Test Lifecycle Callbacks • BeforeAllCallback • BeforeEachCallback • BeforeTestExecutionCallback • TestExecutionExceptionHandler • AfterTestExecutionCallback • AfterEachCallback • AfterAllCallback
32. Roadmap • 5.0 M4 (April 2017): parameterized and repeated tests ✔ • 5.0 M5 (June 2017): dynamic containers, test instance lifecycle management, and minor API changes ✔ • 5.0 M6 (July 2017): Java 9 compatibility, validation (e.g. tag syntax), and bug fixes ✔ • 5.0 RC1, RC2, RC3 (July/August 2017): bug fixes and documentation improvements before GA. ✔ • 5.0 GA (this week, really!): First general availability release • 5.1 (October?): additional features
33. Summary
34. What’s in it for me? • Modern programming model • Powerful extension points • Gentle migration path • Good tool support • Flexible platform/plugin architecture
35. Getting Started User Guide:
 http://junit.org/junit5/docs/current/user-guide/ Sample projects for Gradle and Maven:
 https://github.com/junit-team/junit5-samples Javadoc:
 http://junit.org/junit5/docs/current/api/
36. Wanted: Feedback! Website:
 http://junit.org/junit5/ Code & Issues:
 https://github.com/junit-team/junit5/ Twitter:
 https://twitter.com/junitteam