Set up and Run Junit in a Java project

Set up and Run Junit in a Java project.

set up a gradle project with JUnit

1. Add or update the Java project’s build.gradle file. Add the dependencies.

    plugins {
     id 'java'
     id 'idea'
    }
    sourceCompatibility = '11'
   
    repositories {
     mavenCentral()
    }
   
    dependencies {
     testImplementation('org.junit.jupiter:junit-jupiter:5.5.2')
     compileOnly 'org.projectlombok:lombok:1.18.10'
     annotationProcessor 'org.projectlombok:lombok:1.18.10'
    }
   
    test {
     useJUnitPlatform()
     testLogging {
      events "passed", "skipped", "failed"
     }
    }
   

2. Dependencies

   1. The junit-jupiter-api dependency allows us to write tests and extensions which use JUnit 5.
   2. The junit-jupiter-engine dependency is the main JUnit 5 library which allows us to run tests which use JUnit 5.
   3. The junit-vintage-engine dependency allows us to run tests which use JUnit 3 or

3. Gradle has a native support for JUnit 5, but this support isn’t enabled by default. To enable it:

    test {
        useJUnitPlatform()
    }
   

4. Running Unit Tests With Gradle

    \$ gradle clean test
   

Writting Unit tests using Junit

1. Naming convention

for the class, which follows ClassNameTest. testMethodName

2. Annotations

1. @RunWith annotation - The @RunWith annotation accepts a class name. - The class should extend the org.junit.runner.Runner class. - A runner can change the characteristics of the test class; for example, a Spring runner enables Spring context initialization nature, or a Mockito runner initializes proxy objects annotated with the @Mock annotation.

2. The common test annotations used within a test class (imported from org.junit.jupiter.api) are: - @BeforeAll - executed before all methods in test lass - @BeforeEach - execute before each test method in test class - @Test - actual test method - @AfterEach - executed after each test method in test lass - @AfterAll - executed after all methods in test lass
3. Other basic but useful annotations: - @DisplayName - custom display name for test class or method - @Disabled - disabling test class or method - @RepeatedTest - make a test template out of the test method - @Tag - tag a test class or method for further test selection

import org.junit.jupiter.api.*;

@DisplayName("JUnit5 - Test basics")
class JUnit5Basics {

    @BeforeAll
    static void beforeAll() {
        System.out.println("Before all tests (once)");
    }

    @BeforeEach
    void beforeEach() {
        System.out.println("Runs before each test");
    }

    @Test
    void standardTest() {
        System.out.println("Test is running");
    }

    @Disabled("Failing due to unknown reason")
    @DisplayName("Disabled test")
    @Test
    void disabledTest() {
        System.out.println("Disabled, will not show up");
    }
}

Test Execution Lifecycle

In JUnit 5, by default a new test instance is created for each test method in a test class. This behaviour can be adjusted with class level @TestInstance annotation.

import org.junit.jupiter.api.*;

@TestInstance(TestInstance.Lifecycle.PER_CLASS)
@DisplayName("JUnit5 - Test lifecycle adjustments")
class JUnit5PerClassLifecycle { }

Assertions

JUnit 5 comes with many standard assertions that can be found in org.junit.jupiter.api.Assertions class.

Basic assertions: - assertEquals, - assertArrayEquals, - assertSame, assertNotSame, - assertTrue, - assertFalse, - assertNull, - assertNotNull, - assertLinesMatch, - assertIterablesMatch

Junit best practices

Our test code follows the structure pattern of Arrange-Act-Assert (AAA). Other common patterns include Given-When-Then and Setup-Exercise-Verify-Teardown (Teardown is typically not explicitly needed for unit tests), but we use AAA in this article.

http://wiki.c2.com/?ArrangeActAssert

How to Run a JUnit

1. Maven

    // To run entire test suite:
    mvn test
   
    //To run single/specific test(s):
    mvn -Dtest=TestName test
   

2. Gradle

    //To run entire test suite:
    gradlew test
   
    //To run single/specific test(s):
    gradlew -Dtest.single=testName test
   

Isues

1. Maven does not find JUnit tests to run

https://stackoverflow.com/questions/6178583/maven-does-not-find-junit-tests-to-run

By default Maven uses the following naming conventions when looking for tests to run:

Test* *Test *TestCase Your test class doesn’t follow these conventions. You should rename it or configure Maven Surefire Plugin to use another pattern for test classes.

References

• JUnit Tutorial: Setting Up, Writing, and Running Java Unit Tests
• Tutorialspoint: JUnit - Test Framework
• JUnit 5 - Quick Tutorial
• JUnit 5 User Guide

last update: Dec 2019