JUnit 5 — New Opportunities for Testing on the JVM

JUnit
New Opportunities for Testing on the JVM
Sam Brannen
@sam_brannen

1

@sam_brannen#SpringOne #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

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

Agenda
•  Impetus for Change
•  JUnit 5
•  Demos
•  Live Coding
•  Spring 5
•  Q & A

Show of hands …

Why a new version of JUnit?

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 and …

JUnit 4 Runner API
•  Very powerful
•  In fact, it can do anything
•  But… you can’t combine Runners
•  Parameterized + SpringRunner à no way

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

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

Thanks!

The Kick-off Team

JUnit 5

Roadmap
•  Prototype à December 2nd, 2015
•  5.0.0-ALPHA à February 1st, 2016
•  Milestones & RCs à July 2016 – August 2017
•  5.0.0 GA à September 10th, 2017
•  5.0.1 à October 3rd, 2017
•  5.0.2 à November 12th, 2017 ✅
•  5.1 M1 à November 19th, 2017 🚧

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)

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
•  Java 10
•  We just started building against EA builds recently

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

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

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…

Third-party TestEngines
•  Specsy
•  Spek
•  Cucumber
•  Drools Scenario
•  jqwik
source: https://github.com/junit-team/junit5/wiki/Third-party-Extensions

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

PLATFORM
JUPITER
VINTAGE
PARTY
THIRD

IDEs and Build Tools
•  IntelliJ: ✅ IDEA 2016.2+ (2017.2.5)
•  Eclipse: ✅ Eclipse Oxygen 4.7.1a
•  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

So, what is JUnit Jupiter?

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

Extension APIs
•  BeforeAllCallback
•  BeforeEachCallback
•  BeforeTestExecutionCallback
•  AfterTestExecutionCallback
•  AfterEachCallback
•  AfterAllCallback
•  TestExecutionExceptionHandler
•  ExecutionCondition
•  TestInstancePostProcessor
•  ParameterResolver
•  TestTemplateInvocationContextProvider
Lifecycle Callbacks
Dependency Injection

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

Annotations
•  @Test / @TestFactory and @Testable for TestEngine implementors
•  @RepeatedTest / @ParameterizedTest and @TestTemplate
•  @Nested
•  @TestInstance
•  @BeforeAll / @AfterAll
•  @BeforeEach / @AfterEach
•  @DisplayName
•  @Tag
•  @Disabled

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 bugs in 5.0.0; ﬁxed in 5.0.1and 5.0.2

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.

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

LIVE CODING DEMO
from JUnit 4 to JUnit Jupiter

Tagging
@Tag("fast")
@Test
void myFastTest() {
}
•  Declare @Tag on a test interface, class, or method

Custom Tags
@Target(METHOD)
@Retention(RUNTIME)
@Tag("fast")
public @interface Fast {
}
•  Declare @Tag as a meta-annotation
@Fast
@Test
void myFastTest() {}

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() {
}

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 😱

Dependency Injection
•  Extension Model meets Programming Model
•  ParameterResolver extension API
•  resolves parameters for @Test and lifecycle methods
o  and even constructors
•  can register multiple simultaneously
•  only one wins
•  Use cases
•  server URL, DataSource, Spring ApplicationContext, etc.

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

What’s the significance of @Disabled?

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

LIVE CODING DEMO
tags, display names, dependency injection, & conditions

Testing Traits?

Interface Default Methods
•  Enables the concept of a test interface
•  leading to 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

DEMO
default methods

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

DEMO
nested test classes

Test Templates?

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

@RepeatedTest in Action
@RepeatedTest(5)
void repeatedTest(RepetitionInfo repetitionInfo) {
assertEquals(5, repetitionInfo.getTotalRepetitions());
}
@RepeatedTest(
value = 5,
name = "Wiederholung {currentRepetition} von {totalRepetitions}”
)
void repeatedTestInGerman() {
// ...
}

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

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

@ParameterizedTest in Action
@ParameterizedTest
@ValueSource(strings = {
"mom",
"dad",
"radar",
"racecar",
"able was I ere I saw elba"
})
void palindromes(String candidate) {
assertTrue(isPalindrome(candidate));
}

DEMO
repeated and parameterized tests

Lambdas as Tests?

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 🤓

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)));
}

DEMO
dynamic tests

What’s Missing?
•  Scenario tests
•  Ordering
•  Parallel execution
•  Execution in user-deﬁned thread
•  Declarative and programmatic test suites for the JUnit Platform
•  Java 9 module-path scanning
•  …

LIVE CODING DEMO
custom extensions
•  logging
•  timing
•  conditions

Spring 5 + JUnit 5

Spring Support for JUnit Jupiter
•  Fully integrated in Spring Framework 5.0!
•  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

Configuring JUnit Jupiter with Spring
•  SpringExtension
•  @ExtendWith(SpringExtension.class)
•  @SpringJUnitConfig
•  @ContextConfiguration + SpringExtension
•  @SpringJUnitWebConfig
•  @SpringJUnitConfig + @WebAppConfiguration
•  @EnabledIf / @DisabledIf
•  SpEL expression evaluation for conditional execution

DEMO
Spring 5 and JUnit Jupiter
@EnabledOnMac / @DisabledOnMac

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)

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

In closing …

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

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, …

Demos Used in this Presentation
https://github.com/sbrannen/junit5-demo

Q & A
Sam Brannen
JUnit

JUnit 5 — New Opportunities for Testing on the JVM

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