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JUnit 5 - New Opportunities for Testing on the JVM

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Take a Deep Dive into JUnit 5 with core committer Sam Brannen!

Over the last decade a lot has happened in the world of Java and testing, but JUnit 4 hasn't kept up. Now JUnit 5 is here to help shape the future of testing on the JVM with a focus on Java 8 language features, extensibility, and a modern programming API for testing in Java. Moreover, JUnit isn't just a Java testing framework anymore. Third parties are already developing test engines for Scala, Groovy, Kotlin, etc. that run on the new JUnit Platform.

This session starts off with an overview of the inspiration for & architecture of JUnit 5, from launchers to test engines. Sam will then take the audience on a live coding tour, highlighting support for tagging, custom display names, dependency injection, repeated tests, parameterized tests, conditional test execution, lambda expressions for assertions, assumptions, & dynamic tests, and implementing tests via interface default methods (a.k.a., testing traits).

Next, Sam will present the new extension model in JUnit Jupiter, discussing how to author and register extensions for conditional tests, parameter resolution (a.k.a., dependency injection), lifecycle callbacks, & more.

To round off the session, Sam will quickly showcase the new JUnit Jupiter support in Spring Framework 5.0.

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JUnit 5 - New Opportunities for Testing on the JVM

  1. 1. New Opportunities for Testing on the JVM @sam_brannen JUnit
  2. 2. @sam_brannen#JavaOne #JUnit5 Sam Brannen •  Spring and Java Consultant •  Trainer, Coach, … •  Hardcore developer at heart •  Java Developer for about 20 years •  Spring Framework Core Committer since 2007 •  JUnit 5 Core Committer since October 2015
  3. 3. @sam_brannen#JavaOne #JUnit5 Experts in Spring and Enterprise Java Areas of expertise •  Spring * •  JUnit 5 •  Java EE •  Software Architecture •  Code Reviews Where you find us •  Zurich, Switzerland •  @swiftmind •  http://www.swiftmind.com
  4. 4. @sam_brannen#JavaOne #JUnit5 Agenda •  Impetus for Change •  JUnit 5 •  Spring 5 •  Q & A
  5. 5. @sam_brannen#JavaOne #JUnit5 Show of hands …
  6. 6. @sam_brannen#JavaOne #JUnit5 Why a new version of JUnit?
  7. 7. @sam_brannen#JavaOne #JUnit5 Impetus for Change •  JUnit 4.0 was released a decade ago •  a lot has changed since then… •  testing needs have matured •  expectations have grown •  Modularity à big ball of mud (i.e., only THE junit.jar) •  Test discovery and execution à tightly coupled •  Extensibility à lot of room for improvement •  Let’s not forget Java 8 and Java 9
  8. 8. @sam_brannen#JavaOne #JUnit5 JUnit 4 Runner API •  Very powerful •  In fact, it can do anything •  But… you can’t combine Runners •  Parameterized + SpringRunner à no way
  9. 9. @sam_brannen#JavaOne #JUnit5 JUnit 4… Rules… are meant to be broken •  JUnit 4.7: MethodRule à @Rule •  JUnit 4.9: TestRule à @Rule / @ClassRule •  Great for simple use cases •  Can even be combined •  But… a single rule can’t be used for method-level and class-level callbacks •  Plus… zero support for instance-level callbacks •  Case in point: SpringClassRule / SpringMethodRule
  10. 10. @sam_brannen#JavaOne #JUnit5 JUnit Lambda – Crowdfunding Campaign •  Initiated by Johannes Link and Marc Philipp •  Later joined by Matthias Merdes, Stefan Bechtold, & Sam Brannen •  Ran from July to October 2015 •  Raised 53,937 Euros from 474 individuals and companies •  4 companies donated 6 weeks of developer time
  11. 11. @sam_brannen#JavaOne #JUnit5 Thanks!
  12. 12. @sam_brannen#JavaOne #JUnit5 The Kick-off Team
  13. 13. @sam_brannen#JavaOne #JUnit5 JUnit 5
  14. 14. @sam_brannen#JavaOne #JUnit5 Roadmap •  Prototype à December 2nd, 2015 •  5.0.0-ALPHA à February 1st, 2016 •  6 Milestones à July 2016 – July 2017 •  2-3 Release Candidates à July 2017 – August 2017 •  5.0.0 GA à September 10th, 2017 ✅ •  5.0.1 à Today! (October 3rd, 2017) ✅
  15. 15. @sam_brannen#JavaOne #JUnit5 JUnit 5 – in a Nutshell •  Modular •  Extensible •  Modern •  Forward and backward compatible •  JUnit Platform supports JUnit 3.8, JUnit 4, and JUnit 5 •  New testing frameworks can be run with JUnit 4 infrastructure o  @RunWith(JUnitPlatform.class)
  16. 16. @sam_brannen#JavaOne #JUnit5 JUnit 5 – Java Versions •  Java 8 •  baseline •  but can be used to test application code compiled against previous JDK versions •  Java 9 •  #WorksFineOnJDK9 •  every artifact has a stable AUTOMATIC-MODULE-NAME •  module-path scanning support coming in 5.1
  17. 17. @sam_brannen#JavaOne #JUnit5 JUnit 5 = Platform + Jupiter + Vintage •  JUnit Platform 1.0.0 •  Foundation for launching testing frameworks on the JVM •  Launcher and TestEngine APIs •  ConsoleLauncher, Gradle plugin, Maven Surefire provider •  JUnit Jupiter 5.0.0 •  New programming model and extension model for JUnit 5 •  JUnit Vintage 4.12.0 •  TestEngine for running JUnit 3 and JUnit 4 based tests Revolutionary Evolutionary Necessary
  18. 18. @sam_brannen#JavaOne #JUnit5 Launcher API •  Used by IDEs and build tools to launch the framework •  Central API for discovering and executing tests via one or more engines •  LauncherDiscoveryRequest •  selectors and filters •  Feedback provided via the TestExecutionListener API •  ConsoleLauncher for command-line support
  19. 19. @sam_brannen#JavaOne #JUnit5 TestEngine API •  Test engine discovers and executes tests •  for a particular programming model •  Automatic registration via Java’s ServiceLoader mechanism •  JupiterTestEngine •  VintageTestEngine •  Implement your own…
  20. 20. @sam_brannen#JavaOne #JUnit5 Third-party TestEngines •  Specsy •  Spek •  Cucumber •  Drools Scenario •  jqwik source: https://github.com/junit-team/junit5/wiki/Third-party-Extensions
  21. 21. P L A T F O R M J U P I T E RV I N T A G E P A R T Y T H I R D
  22. 22. PLATFORM JUPITER VINTAGE PARTY THIRD
  23. 23. @sam_brannen#JavaOne #JUnit5 IDEs and Build Tools •  IntelliJ: ✅ IDEA 2016.2+ •  Eclipse: ✅ Eclipse Oxygen 4.7.1a (to be released next week) •  NetBeans: 🙉🙈🙊 •  Gradle: interim solution from JUnit Team •  to be taken over by Gradle team (end of 2017) •  Android JUnit 5: third-party Android support •  Maven: interim solution from JUnit Team •  being taken over by Maven Surefire team See user guide and sample apps for examples
  24. 24. @sam_brannen#JavaOne #JUnit5 JUnit Jupiter – Extension Model •  Extension •  marker interface •  org.junit.jupiter.api.extension •  package containing all extension APIs •  implement as many as you like •  @ExtendWith(...) •  used to register one or more extensions •  interface, class, or method level o  or as a meta-annotation
  25. 25. @sam_brannen#JavaOne #JUnit5 Extension APIs •  BeforeAllCallback •  BeforeEachCallback •  BeforeTestExecutionCallback •  AfterTestExecutionCallback •  AfterEachCallback •  AfterAllCallback •  TestExecutionExceptionHandler •  ExecutionCondition •  TestInstancePostProcessor •  ParameterResolver •  TestTemplateInvocationContextProvider Lifecycle Callbacks Dependency Injection
  26. 26. @sam_brannen#JavaOne #JUnit5 JUnit Jupiter – Programming Model org.junit.jupiter.api (org.junit.jupiter.params) •  Annotations and meta-annotations •  Assertions and Assumptions •  Custom display names •  Visibility •  Tagging •  Conditional test execution •  Dependency injection for constructors and methods •  Lambda expressions and method references •  Interface default methods •  Nested test classes •  Repeated tests, parameterized tests, dynamic tests
  27. 27. @sam_brannen#JavaOne #JUnit5 Annotations •  @Test / @TestFactory and @Testable for TestEngine implementors •  @RepeatedTest / @ParameterizedTest and @TestTemplate •  @Nested •  @TestInstance •  @BeforeAll / @AfterAll •  @BeforeEach / @AfterEach •  @DisplayName •  @Tag •  @Disabled
  28. 28. @sam_brannen#JavaOne #JUnit5 JUnit 4 Rule Migration Support •  @EnableRuleMigrationSupport o  located in experimental junit-jupiter-migrationsupport module o  registers 3 extensions for JUnit Jupiter •  ExternalResourceSupport o  TemporaryFolder, etc. •  VerifierSupport o  ErrorCollector, etc. •  ExpectedExceptionSupport o  ExpectedException o  minor bug in 5.0.0; fixed in 5.0.1
  29. 29. @sam_brannen#JavaOne #JUnit5 Assertions org.junit.jupiter.api.Assertions •  Limited set of core assertions •  assertEquals(), assertNotNull(), etc. •  assertThrows() – λ •  assertTimeout() and assertTimeoutPreemptively() – λ •  assertAll() – λ •  Supplier<String> à λ for lazy failure message evaluation •  message is now the last parameter •  For more power, use AssertJ, Hamcrest, etc.
  30. 30. @sam_brannen#JavaOne #JUnit5 Assumptions org.junit.jupiter.api.Assumptions •  Limited set of core assumptions •  For aborting tests mid-flight •  Otherwise, favor a custom ExecutionCondition for skipping •  assumeTrue() / assumeFalse() •  BooleanSupplier, Supplier<String> – λ •  assumingThat( ? , () -> {} ); – λ
  31. 31. @sam_brannen#JavaOne #JUnit5 LIVE CODING DEMO from JUnit 4 to JUnit Jupiter
  32. 32. @sam_brannen#JavaOne #JUnit5 Tagging @Tag("fast") @Test void myFastTest() { } •  Declare @Tag on a test interface, class, or method
  33. 33. @sam_brannen#JavaOne #JUnit5 Custom Tags @Target(METHOD) @Retention(RUNTIME) @Tag("fast") public @interface Fast { } •  Declare @Tag as a meta-annotation @Fast @Test void myFastTest() {}
  34. 34. @sam_brannen#JavaOne #JUnit5 Composed Tags @Target(METHOD) @Retention(RUNTIME) @Tag("fast") @Test public @interface FastTest { } •  Declare @Tag as a meta-annotation with other annotations (JUnit, Spring, etc.) @FastTest void myFastTest() { }
  35. 35. @sam_brannen#JavaOne #JUnit5 Test Names •  Names default to test class or test method names •  characters limited based on Java syntax •  Custom display names à @DisplayName •  Can contain spaces, special chars, and even emoji 😱
  36. 36. @sam_brannen#JavaOne #JUnit5 Dependency Injection •  Extension Model meets Programming Model •  ParameterResolver extension API •  resolves parameters for constructors or method o  not just @Test and lifecycle methods •  can register multiple simultaneously •  only one wins •  Use cases •  server URL, DataSource, Spring ApplicationContext, etc.
  37. 37. @sam_brannen#JavaOne #JUnit5 TestInfo •  TestInfo: inject into constructor, @Test, @BeforeEach, etc. •  access display name, tags, class, method •  TestInfoParameterResolver •  eating our own dog food ;-) •  See also: •  RepetitionInfo for @RepeatedTest •  TestReporter •  MockitoExtension •  SpringExtension
  38. 38. @sam_brannen#JavaOne #JUnit5 LIVE CODING DEMO tags, display names, and dependency injection
  39. 39. @sam_brannen#JavaOne #JUnit5 Conditional Test Execution •  Extension Model meets Programming Model •  ExecutionCondition •  @Disabled •  DisabledCondition •  eating our own dog food ;-) •  Deactivate via Launcher, system property, or junit-platform.properties file •  junit.conditions.deactivate = org.junit.* Game Changer
  40. 40. @sam_brannen#JavaOne #JUnit5 Interface Default Methods •  Introduces the concept of a test interface •  Enables multiple inheritance in tests •  a.k.a., testing traits •  @BeforeAll / @AfterAll •  if using @TestInstance(Lifecyle.PER_CLASS) •  @BeforeEach / @AfterEach •  @Test / @RepeatedTest / @ParameterizedTest / @TestFactory •  @Tag •  @ExtendWith •  See StringTests and TestInterfaceDemo examples in user guide
  41. 41. @sam_brannen#JavaOne #JUnit5 DEMO default methods
  42. 42. @sam_brannen#JavaOne #JUnit5 Nested Test Classes •  Enables logical, hierarchical grouping of test classes •  with shared initialization and state from outer classes •  Declare @Nested on non-static nested classes •  i.e., inner classes •  You can even combine nested classes and test interfaces •  See TestingAStack example in user guide and Bowling Game Kata by Tim Riemer
  43. 43. @sam_brannen#JavaOne #JUnit5 DEMO nested test classes
  44. 44. @sam_brannen#JavaOne #JUnit5 Repeated Tests •  Annotate a method with @RepeatedTest instead of @Test o  and specify the number of repetitions •  Optionally have the RepetitionInfo injected as a method parameter •  Optionally override the display name
  45. 45. @sam_brannen#JavaOne #JUnit5 @RepeatedTest in Action @RepeatedTest(5) void repeatedTest(RepetitionInfo repetitionInfo) { assertEquals(5, repetitionInfo.getTotalRepetitions()); } @RepeatedTest( value = 5, name = "Wiederholung {currentRepetition} von {totalRepetitions}” ) void repeatedTestInGerman() { // ... }
  46. 46. @sam_brannen#JavaOne #JUnit5 Parameterized Tests (junit-jupiter-params) •  Annotate a method with @ParameterizedTest instead of @Test o  and specify the source of the arguments o  optionally override the display name •  Sources o  @ValueSource: String, int, long, double o  @EnumSource o  @MethodSource o  @CsvSource & @CsvFileSource o  @ArgumentsSource & custom ArgumentsProvider
  47. 47. @sam_brannen#JavaOne #JUnit5 Argument Conversion •  Implicit conversion o  Primitive types and their wrappers o  Enums o  java.time types (JSR-310) •  Explicit conversion o  @ConvertWith and custom ArgumentConverter o  @JavaTimeConversionPattern built-in support for JSR-310
  48. 48. @sam_brannen#JavaOne #JUnit5 @ParameterizedTest in Action @ParameterizedTest @ValueSource(strings = { "mom", "dad", "radar", "racecar", "able was I ere I saw elba" }) void palindromes(String candidate) { assertTrue(isPalindrome(candidate)); }
  49. 49. @sam_brannen#JavaOne #JUnit5 LIVE CODING DEMO repeated and parameterized tests
  50. 50. @sam_brannen#JavaOne #JUnit5 Dynamic Tests •  Conventional tests are static (i.e., known at compile time) •  @Test •  A DynamicTest is registered at runtime – λ •  as lambda expression in a stream, collection, etc. •  by a method annotated with @TestFactory •  Can also register a DynamicContainer for dynamic nesting •  Somewhat analogous to parameterized tests •  just more… dynamic 🤓
  51. 51. @sam_brannen#JavaOne #JUnit5 Dynamic Tests in Action @TestFactory Stream<DynamicTest> dynamicTestsFromIntStream() { // Generates tests for the first 10 even integers. return IntStream.iterate(0, n -> n + 2) .limit(10) .mapToObj(n -> dynamicTest("test" + n, () -> assertTrue(n % 2 == 0))); }
  52. 52. @sam_brannen#JavaOne #JUnit5 DEMO dynamic tests
  53. 53. @sam_brannen#JavaOne #JUnit5 What’s Missing? •  Scenario tests •  Ordering •  Parallel execution •  Execution in user-defined thread •  Declarative test suites for the JUnit Platform •  Java 9 module-path scanning •  …
  54. 54. @sam_brannen#JavaOne #JUnit5 Spring 5 + JUnit 5
  55. 55. @sam_brannen#JavaOne #JUnit5 Spring Support for JUnit Jupiter •  Fully integrated in Spring Framework 5.0! •  released last week 😎 •  Supports all Core Spring TestContext Framework features •  Constructor and method injection via @Autowired, @Qualifier, @Value •  Conditional test execution via SpEL expressions •  ApplicationContext configuration annotations •  Also works with Spring Framework 4.3 https://github.com/sbrannen/spring-test-junit5
  56. 56. @sam_brannen#JavaOne #JUnit5 Configuring JUnit Jupiter with Spring •  SpringExtension •  @ExtendWith(SpringExtension.class) •  @SpringJUnitConfig •  @ContextConfiguration + SpringExtension •  @SpringJUnitWebConfig •  @SpringJUnitConfig + @WebAppConfiguration •  @EnabledIf / @DisabledIf •  SpEL expression evaluation for conditional execution
  57. 57. @sam_brannen#JavaOne #JUnit5 DEMO Spring 5 and JUnit Jupiter @EnabledOnMac / @DisabledOnMac
  58. 58. @sam_brannen#JavaOne #JUnit5 Spring Boot 1.4 + JUnit 5 – Custom Config @Target(TYPE) @Retention(RUNTIME) @ExtendWith(SpringExtension.class) @SpringBootTest(webEnvironment = MOCK) @AutoConfigureMockMvc @Transactional public @interface SpringEventsWebTest { } •  @SpringBootTest + @AutoConfigureMockMvc + @ExtendWith(SpringExtension.class)
  59. 59. @sam_brannen#JavaOne #JUnit5 Spring Boot 1.4 + JUnit 5 – MockMvc Test @SpringEventsWebTest class EventsControllerTests { @Test @DisplayName("Home page should display more than 10 events") void listEvents(@Autowired MockMvc mockMvc) throws Exception { mockMvc.perform(get("/")) .andExpect(view().name("event/list")) .andExpect(model().attribute("events", hasSize(greaterThan(10)))); } } •  @SpringEventsWebTest + method-level DI + MockMvc
  60. 60. @sam_brannen#JavaOne #JUnit5 In closing …
  61. 61. @sam_brannen#JavaOne #JUnit5 JUnit 5 Resources Project Homepage à http://junit.org/junit5 User Guide à http://junit.org/junit5/docs/current/user-guide Javadoc à http://junit.org/junit5/docs/current/api GitHub à https://github.com/junit-team Gitter à https://gitter.im/junit-team/junit5 Stack Overflow à http://stackoverflow.com/tags/junit5
  62. 62. @sam_brannen#JavaOne #JUnit5 Spring Resources Spring Framework à http://projects.spring.io/spring-framework Spring Guides à http://spring.io/guides Spring JIRA à https://jira.spring.io Spring on GitHub à https://github.com/spring-projects/spring-framework Stack Overflow à spring, spring-test, spring-mvc, spring-boot, …
  63. 63. @sam_brannen#JavaOne #JUnit5 Additional JUnit 5 Talks @ JavaOne 2017 JUnit 5 BOF Tuesday, Oct 03, 6:45 p.m. - 7:30 p.m. | Moscone West - Room 2016 JUnit5: Features, Architecture, and Extensibility Wednesday, Oct 04, 2:45 p.m. - 3:30 p.m. | Moscone West - Room 2009
  64. 64. @sam_brannen#JavaOne #JUnit5 Demos Used in this Presentation https://github.com/sbrannen/junit5-demo
  65. 65. @sam_brannen#JavaOne #JUnit5 Q & A Sam Brannen JUnit

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