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Junit 5: Features, Architecture, and Extensibility - http://bit.ly/psu-junit5-j1

JUnit 5

Steve MoyerSteve Seltzer

Niraja Ramesh

The Pennsylvania State University

Features, Architecture, and Extensibility

About Us

● Steve Moyer– Enterprise Architect

● Steve Seltzer– Programmer/Analyst

● Niraja Ramesh– Programmer/Analyst

About Us● Enterprise Infrastructure and Operations

● Core IT support organization for Penn State

● Software Engineering Unit

Agenda

● Rationale● Architecture● Principles● Features● Code examples● Future directions ● References

Rationale

● Decouple test execution and reporting from test definition and provisioning

● Rethinking the JUnit’s extensibility story● Support for Java 8 features (Lambdas, Streams,

Interface default methods) for better assertions, generating test cases, formulating test hierachies, testing asynchronous code and other stuff

Architecture

What do I need?

● junit-jupiter-api – to compile test classes and/or extensions

● junit-jupiter-engine (and dependencies) – to run JUnit 5 tests

● junit-vintage-engine (and dependencies) – to run JUnit 4 tests (using JUnit 5)

What do I need?

● junit-platform-console (and dependencies) – to execute JUnit 5 tests from the command line

● junit-platform-runner (and dependencies) – to execute JUnit 5 tests using JUnit 4

– provides a way to run JUnit 5 tests in Eclipse and (some) other tools that don’t yet natively support JUnit 5.

What do I need?

● junit-platform-maven-provider – to execute tests using JUnit 5 during a Maven build.

– See the Maven example at: https://github.com/junit-team/junit5-samples/tree/master/junit5-maven-consumer

● junit-platform-gradle-plugin – to execute tests using JUnit 5 during a Gradle build.

– See the Gradle example at: https://github.com/junit-team/junit5-samples/tree/master/junit5-gradle-consumer

Set upplugin

https://github.com/PennState/junit5-presentation/blob/master/pom.xml

Set updependencies

Principles

● Prefer extension points over features● An extension point should be good at one thing● It should be hard to write tests that behave

differently based on how they are run● Tests should be easy to understand● Minimize dependencies (especially third-party)

https://github.com/junit-team/junit5/wiki/Core-Principles

Features

● Meta-Annotations ● Tags and filters● Dependency injection through parameters

on constructors and methods● Interface default methods● Dynamic tests (runtime)● Extensions

Features● API Isolation

– Jupiter API for writing tests and extensions

– Engine API for writing new engines

● API Evolution– API annotations

● Internal ● Deprecated● Experimental ● Maintained ● Stable

Code Examples

Code Examples● Assertion tests● Exception tests● Assumption tests● Meta-Annotation● Dynamic tests● Extension tests● Grouped tests● Nested tests

Assertions

Assertion TestsSimple Assertions

Junit 4 Junit 5

assert...(expected, actual) assert...(expected, actual)

assert...(message, expected, actual) assert...(expected, actual, message)

Assertion TestsSimple Assertions

Assertion Tests

AssertionTests.java

Maven Output

output - txt file

output - xml file

maven console output

Available Assertions

http://junit.org/junit5/docs/current/api/org/junit/jupiter/api/Assertions.html

● assertTrue

● assertFalse

● assertEquals

● assertNotEquals

● assertArrayEquals

● fail

● assertNull

● assertNotNull

● assertSame

● assertNotSame

● assertAll

● assertThrows

● expectThrows

Exception Tests

ExceptionTests.java

Exception Tests

SampleStudents.java

The class builds data models for freshman, part-time, full-time and so forth.

Exception Tests

BuildTestCourses.java

This class creates different courses that we will register the students throughout our tests.

Exception Tests

CourseUtils.java

This class registers courses for the students.Throws exception if their total credits exceed MAX_ALLOWED.

Exception Tests

Total credits for all courses exceed 25‘registerForCourse’ method throws an exception

assertThrows compares the thrown exception class to the expected one

ExceptionTests.java

Exception Tests

ExceptionTests.java

Assumptions

Assumptions Tests

● assumeTrue● assumeFalse● assumingThat

Assumption TestsassumeTrue

AssumptionTests.java

Assumptions Test

assumeFalse

Assumptions TestassumingThat

Meta-Annotations

Meta-Annotation

UseridCaseTests.java

Tagging & Filtering

TaggingTest.java

Dynamic Tests

Dynamic Test

● Test case generated at run-time by a factory method @TestFactory

● Composed of a display name and an Executable● Executable is a functional interface – meaning tests

can be provided as lambda expressions or method references

● Because of dynamic nature, lifecycle callbacks are not applicable

Dynamic Testing

DynamicTests.java

Extensibility

Extension Points

● ParameterResolver● ContainerExecutionCondition● TestExecutionCondition● TestInstancePostProcessor

● BeforeAllCallback● AfterAllCallback● BeforeEachCallback● AfterEachCallback● BeforeTestExecutionCallback● AfterTestExecutionCallback

http://junit.org/junit5/docs/current/api/org/junit/jupiter/api/extension/Extension.html

Extension PointTestExecutionCondition

Extension Test

This class disables a test if the method name does not contain the word ‘affiliate’

AfflliateDetector.java

implements TestExecutionCondition

Extension Test

Class ExtensionDisabledTests contains a method that will return a boolean indicating whether method name contains the word ‘student’

Register AffiliateDetector extension via @ExtendWith

ExtensionDisabledTests.java

implements TestExecutionCondition

ExtensionDisabledTests.java

Contains “Affiliate” (passes TestExecutionCondition)Contains “Student” (passes studentDetector method )

Contains “Affiliate” (passes TestExecutionCondition)No “Student” (fails studentDetector method )

implements TestExecutionConditionExtension Test

No “Affiliate” (fails TestExecutionCondition)

Extension PointParameterResolver

Built-in ParameterResolvers

● TestInfo– If a method parameter of type TestInfo is

resolved, JUnit will supply an instance that allows a test to retrieve the display name, tags, test class and test method.

● TestReporter– If a method parameter of type

TestReporter is resolved, JUnit will supply an instance that allows a test to publish entries to the output report.

Extension Test

looks for @UseridTest annotation to return true/false

returns value for given parameters(in the example, a String and a boolean)

UseridParameterResolver.java

implements ParameterResolver

Extension Test

UseridCaseTests.java

implements ParameterResolver

Extension PointCallbacks

Extension Tests

Extension Test

ChildTests – extends ParentTests

ParentTests – registers extension with class implementing callbacks

class implementing callbacks

Callback Example

implements Callback

Each class prints out the methods available within that class

Extension Testsimplements Callback

Grouped Tests

● Traditional For Loop● assertAll()● Factory Tests (@TestFactory)

Collection Testing

Halts test execution when course prerequisite is found

LoopingTests.java

AssertAll

Executes all test cases inside the assertAll block

LoopingTests.java

Factory Test

Executes all tests regardless of failures

LoopingTests.java

Nested Tests

FakeSuiteTests.java

Future Directions

Future

● M3 (September 30, 2016)– JUnit 4 interoperability

– Additional discovery selectors

– Documentation

● M4 (October 30, 2016)– Parameterized tests

– Enhanced dynamic tests

Future

● M5 (November 29, 2016)– Scenario tests

– Repeated tests

– Test execution in user-defined thread

Questions / Comments?

References

References● This presentation

– See the presentation at: http://bit.ly/psu-junit5-j1

– See the code samples at: http://bit.ly/psu-junit5-j1-code

● JUnit 5– Users guide Current Milestone, SNAPSHOT

– Javadocs Current Milestone, SNAPSHOT

– Code and issues Github

References

● Articles– Voxxed “JUnit 5 – Setup”

– Voxxed “JUnit 5 – The Basics”

– Voxxed “JUnit 5 – Architecture”

– Voxxed “J Unit 5 – Extension Model”

● Presentations– vJUG “JUnit 5: Next Generation Testing on the JVM”

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