JUnit 5: What's New and What's Coming - Spring I/O 2019

Sam Brannen
@sam_brannen
JUnit

2@sam_brannen #JUnit5 #springio19
Sam Brannen
• Principal Software Engineer
• Java Developer for over 20 years
• Spring Framework Core Committer since 2007
• JUnit 5 Core Committer since October 2015

@sam_brannen #JUnit5 #springio19 3
Agenda
JUnit 5
JUnit Jupiter
Migrating from JUnit 4
New Features since 5.0
Roadmap
Spring and JUnit Jupiter
Q & A

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

JUnit 5 = Platform + Jupiter + Vintage
• JUnit Platform
• Foundation for launching testing frameworks on the JVM
• Launcher and TestEngine APIs
• ConsoleLauncher
• JUnit Jupiter
• New programming model & extension model for JUnit 5
• JUnit Vintage
• TestEngine for running JUnit 3 & JUnit 4 based tests
Revolutionary
Evolutionary
Necessary

In a Nutshell, JUnit 5 is …
• Complete rewrite of JUnit
• Improving on what JUnit 4 had to offer
• With extensibility in mind
• Modular, Extensible, & Modern
• Forward and backward compatible
• JUnit Platform supports JUnit 3.8, JUnit 4, and JUnit Jupiter
• Plus support for any TestEngine imaginable

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

Java Versions
Baseline
• AUTOMATIC-MODULE-NAM
E
• module-path scanning
Building and testi
ng against 11 and
12

IDEs and Build Tools
• IntelliJ: since IDEA 2016.2+
• Eclipse: since Eclipse Oxygen 4.7.1a+
• NetBeans: since Apache NetBeans 10.0
• Gradle: official test task support since Gradle 4.6
• Maven: official support since Maven Surefire 2.22.0
• Ant: junitlauncher task since Ant 1.10.3
See user guide and
sample apps for
examples

Releases
Version Date
5.0.0 September 10th, 2017
5.1.0 February 18th, 2018
5.2.0 April 29th, 2018
5.3.0 September 3rd, 2018
5.4.0 February 7th, 2019
5.4.2 April 7th, 2019

In a Nutshell, JUnit Jupiter is …
“The new programming model and extension model in JUnit 5”
• Programming Model
• How you write tests
• Annotations
• Assertions
• Assumptions
• Types of tests
• Extension Model
• How you and third parties extend the framework
• Spring, Mockito, Selenium, …

More Powerful Programming Model
What you can do with JUnit Jupiter that you can’t do with JUnit 4.
• Visibility
• Everything does not have to be public
• Custom display names
• @DisplayName: spaces, special characters, emoji 😱
• DisplayNameGenerator (since 5.4)
• Tagging
• @Tag replaces experimental @Category
• Tag Expression Language (since 5.1)

Example: CalculatorTests
@DisplayName("Calculator Unit Tests")
class CalculatorTests {
private final Calculator calculator = new Calculator();
@Test
@DisplayName("➕")
void add() {
assertEquals(5, calculator.add(2, 3),
() -> "2 + 3 = " + (2 + 3));
}
// ...
}

Expected Exceptions
@Test
@DisplayName("n ➗ 0 → ArithmeticException")
void divideByZero() {
Exception exception = assertThrows(ArithmeticException.class,
() -> calculator.divide(1, 0));
assertEquals("/ by zero", exception.getMessage());
}

Timeouts
@Test
@DisplayName("Ensure Fibonacci computation is 'fast enough'")
void fibonacci() {
// assertTimeout(ofMillis(1000),
// () -> calculator.fibonacci(30));
assertTimeoutPreemptively(ofMillis(1000),
() -> calculator.fibonacci(30));
}

Even More Power and Expressiveness
• Meta-annotation support
• Create your own custom composed annotations
• Combine annotations from Spring and JUnit
• Conditional test execution
• Dependency injection for constructors and methods
• Lambda expressions and method references
• Interface default methods and testing traits
• @Nested test classes
• @RepeatedTest, @ParameterizedTest, @TestFactory
• @TestInstance lifecycle management

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() {}

@RepeatedTest,
@ParameterizedTest, @TestFactory

@RepeatedTest
@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: char, short, byte, int, long, float, double, String, Class
o @NullSource, @EmptySource, and @NullAndEmptySource (since 5.4)
o @EnumSource
o @MethodSource
o @CsvSource & @CsvFileSource
o @ArgumentsSource & custom ArgumentsProvider

Argument Conversion and Aggregation
• Implicit conversion
o Primitive types and their wrappers
o Enums
o File, URL, Currency, Locale, …
o java.time types (JSR-310)
o factory constructor or static factory method
• Explicit conversion
o @ConvertWith and custom ArgumentConverter
o @JavaTimeConversionPattern built-in support for JSR-310
• Argument Aggregation (since 5.2)
o Arguments and ArgumentAggregator

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

@ParameterizedTest – @MethodSource
@ParameterizedTest
@MethodSource // ("palindromes")
void palindromes(String candidate) {
assertTrue(isPalindrome(candidate));
}
static Stream<String> palindromes() {
return Stream.of("mom",
"dad",
"radar",
"racecar",
"able was I ere I saw elba");
}

Dynamic Tests
@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
repeated, parameterized, and dynamic tests

Configuring Parallelism (5.3)
• Set junit.jupiter.execution.parallel.enabled config param to true
o in junit-platform.properties
o via Launcher API
o as JVM system property
• Configure the junit.jupiter.execution.parallel.config.strategy
o dynamic (the default)
o fixed
o custom

Execution Mode and Synchronization (5.3)
• Disable parallel execution on a per test basis
o @Execution(SAME_THREAD) // or CONCURRENT
• Control synchronization
o @ResourceLock("myResource") // default READ_WRITE
o @ResourceLock(value = "myResource", mode = READ)

DEMO
ParameterizedFibonacciTests

New 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
• @RegisterExtension
• programmatic registration via fields (since 5.1)

Extension APIs – Lifecycle Callbacks
• BeforeAllCallback
• BeforeEachCallback
• BeforeTestExecutionCallback
• AfterTestExecutionCallback
• AfterEachCallback
• AfterAllCallback
Extensions wrap
user-supplied
lifecycle methods
and test methods

Extension APIs – Miscellaneous
• ExecutionCondition
• TestInstanceFactory (since 5.3)
• TestInstancePostProcessor
• ParameterResolver
• TestTemplateInvocationContextProvider
• TestExecutionExceptionHandler
• TestWatcher (since 5.4)
• DisplayNameGenerator (since 5.4)
• MethodOrderer (since 5.4)
Dependency Injectio
n
Applied during the
discovery phase

DisplayNameGenerator (5.4)
• SPI for generating custom display names for classes and methods
• Configured via @DisplayNameGeneration
• Implement your own
• Or use a built-in implementation:
• Standard: default behavior
• ReplaceUnderscores: replaces underscores with spaces

MethodOrderer (5.4)
• API for controlling test method execution order
• Configured via @TestMethodOrder
• Implement your own
• Or use a built-in implementation:
• Alphanumeric: sorted alphanumerically
• OrderAnnotation: sorted based on @Order
• Random: pseudo-random ordering

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, JVM system property, or the
junit-platform.properties file
• junit.conditions.deactivate = org.junit.*
Game Changer

Built-in Conditions (5.1)
• @Disabled (since 5.0)
• @EnabledIf / @DisabledIf (may soon be deprecated)
• @EnabledOnJre / @DisabledOnJre
• @EnabledOnOs / @DisabledOnOs
• @EnabledIfSystemProperty / @DisabledIfSystemProperty
• @EnabledIfEnvironmentVariable / @DisabledIfEnvironmentVariable

Do I have to migrate from JUnit 4 to JUnit 5?
• Yes and No…
• You can run JUnit 4 tests on the JUnit Platform via the VintageTestEngine
• You can run JUnit 4 tests alongside JUnit Jupiter tests
o In the same project
• You can gradually migrate existing JUnit 4 tests to JUnit Jupiter
o if you want to
o or… you can just write all new tests in JUnit Jupiter

Annotations, Assertions, Assumptions
• @org.junit.Test  @org.junit.jupiter.api.Test
• @Ignore  @Disabled
• @BeforeClass / @AfterClass  @BeforeAll / @AfterAll
• @Before / @After  @BeforeEach / @AfterEach
• org.junit.Assert  org.junit.jupiter.api.Assertions
• org.junit.Assume  org.junit.jupiter.api.Assumptions
Failure message n
ow comes LAST!

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

JUnit 4 @Ignore and Assumption Support
(5.4)
• @EnableJUnit4MigrationSupport
o registers the IgnoreCondition
o supports @Ignore analogous to @Disabled
o includes @EnableRuleMigrationSupport semantics
• JUnit Jupiter supports JUnit 4 assumptions
o methods in org.junit.Assume
o AssumptionViolatedException

• JUnit Maven BOM
• Parallel test execution
• Output capture for System.out and System.err
• Tag expression language
• Custom test sources for dynamic tests
• Improved Kotlin support
• Numerous enhancements for parameterized tests
• Built-in @Enable* / @Disable* conditions
• @RegisterExtension
• TestInstanceFactory
• …

• New junit-jupiter dependency aggregating artifact
• XML report generating listener
• Test Kit for testing engines and extensions
• null and empty argument sources for @ParameterizedTest methods
• @TempDir support for temporary directories
• DisplayNameGenerator SPI
• TestWatcher extension API
• Ordering for @Test methods and @RegisterExtension fields
• Improved JUnit 4 migration support for assumptions and @Ignore
• …

Coming in JUnit 5.5
• Boolean values in @ValueSource
• Repeatable annotations for built-in conditions
• Declarative, preemptive timeouts for tests in JUnit Jupiter
• New InvocationInterceptor extension API
• execution in a user-defined thread
• Configurable test discovery implementation for test engines
• …

The 5.x Backlog
• Custom ClassLoader
• Programmatic extension management
• Declarative and programmatic test suites for the JUnit Platform
• Parameterized test classes
• Scenario tests
• New XML / JSON reporting format
• …

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

Automatic Test Constructor Autowiring (5.2)
• By default, a test class constructor must be annotated with @Autowired
• The ”default” can be changed
• set spring.test.constructor.autowire=true
• JVM system property or SpringProperties mechanism
• @TestConstructor(autowire = true/false)
• Overrides default on a per-class basis

Spring Boot 2.1 & JUnit Jupiter – Custom
Config
@Target(TYPE)
@Retention(RUNTIME)
// @ExtendWith(SpringExtension.class)
@SpringBootTest
@AutoConfigureMockMvc
@Transactional
public @interface SpringEventsWebTest {
}
• @SpringBootTest + @AutoConfigureMockMvc +
@ExtendWith(SpringExtension.class)

Spring Boot 2.1 & JUnit Jupiter – 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

Tip: Upgrading JUnit 5 Version in Spring Boot
• Popular question…
• https://stackoverflow.com/a/54605523/388980
• Gradle:
ext['junit-jupiter.version']='5.4.2'
• Maven:
<properties>
<junit-jupiter.version>5.4.2</junit-jupiter.version>
</properties>

How can I help out?
• Participate on GitHub
• Report issues
• Suggest new features
• Participate in discussions
• Answer questions on Stack Overflow and Gitter
• Support the JUnit Team with donations via Steady HQ
https://steadyhq.com/en/junit

JUnit 5 Resources
Project Homepage  http://junit.org/junit5
User Guide  http://junit.org/junit5/docs/current/user-guide
Javadoc  http://junit.org/junit5/docs/current/api
GitHub  https://github.com/junit-team
Gitter  https://gitter.im/junit-team/junit5
Stack Overflow  http://stackoverflow.com/tags/junit5

Demos Used in this Presentation
https://github.com/sbrannen/junit5-demo
https://github.com/junit-team/junit5/tree/master/documentation/src/test

Sam Brannen
@sam_brannen
Thanks!
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JUnit 5: What's New and What's Coming - Spring I/O 2019

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