JUnit 5

About

JUnit 5, also known as JUnit Jupiter, is the latest version of the JUnit framework. It offers a more modular and flexible architecture compared to JUnit 4. JUnit 5 consists of three main modules:

1. JUnit Jupiter: Provides new programming and extension models for writing tests and extensions in JUnit 5.

2. JUnit Vintage: Provides a TestEngine for running JUnit 3 and JUnit 4 based tests on the JUnit Platform.

3. JUnit Platform: Serves as a foundation for launching testing frameworks on the JVM. It defines the TestEngine API for developing new testing frameworks that run on the platform.

Core Concepts

• Jupiter Extensions: JUnit 5 leverages extensions for advanced test functionalities like parameterized tests, test lifecycle management, dependency injection, and more.

• Annotations: It utilizes annotations like @Test, @BeforeEach, @AfterEach, and others from the org.junit.jupiter.api package for defining test cases and behavior.

• Assertions: JUnit 5 offers assertions (like assertEquals, assertTrue) similar to JUnit 4 for verifying expected test outcomes.

• Test Engine: It separates test execution logic from the annotations, allowing different testing frameworks to integrate with JUnit 5 through the TestEngine API.

Key Features

• Modular Design: The use of extensions promotes a modular approach, enabling customization and tailoring testing experiences based on project needs.

• Improved Readability: Annotations like @Test and @BeforeEach enhance test code readability and maintainability.

• Support for Lambda Expressions (Java 8+): JUnit 5 takes advantage of features like lambdas for concise and expressive test code (requires Java 8 or above).

• Parameterized Tests: This feature allows running the same test with different sets of data, improving test efficiency and coverage.

• Dynamic Tests: JUnit 5 supports creating tests dynamically at runtime based on certain conditions.

• Integration with Build Tools and IDEs: It integrates seamlessly with popular build tools like Maven and Gradle, as well as IDEs like IntelliJ IDEA and Eclipse, for a smooth testing workflow.

Benefits of Using JUnit 5

• Enhanced Developer Experience: The modular design and powerful features make writing and managing unit tests more efficient and enjoyable.

• Improved Code Quality: JUnit 5 encourages writing clean, well-tested, and maintainable code.

• Faster Feedback: Features like parameterized tests and dynamic tests enable faster test execution and feedback cycles.

• Increased Confidence: JUnit 5 helps ensure core functionalities work as intended, leading to more robust applications.

Integration with Maven

POM Dependency

<dependencies>
    <!-- Junit Jupiter API and Engine -->
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-api</artifactId>
        <version>5.9.3</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-engine</artifactId>
        <version>5.9.3</version>
        <scope>test</scope>
    </dependency>
    
    <!-- Junit Vintage Engine for running JUnit 3 and JUnit 4 tests -->
    <dependency>
        <groupId>org.junit.vintage</groupId>
        <artifactId>junit-vintage-engine</artifactId>
        <version>5.9.3</version>
        <scope>test</scope>
    </dependency>
    
    <!-- Optional: Junit Platform Runner -->
    <dependency>
        <groupId>org.junit.platform</groupId>
        <artifactId>junit-platform-runner</artifactId>
        <version>1.9.3</version>
        <scope>test</scope>
    </dependency>
</dependencies>

JUnit 4 Maven Plugin (Optional)

The Maven Surefire plugin, typically already included in most Maven projects, is responsible for executing tests during the build lifecycle. While not strictly necessary for basic JUnit 5 usage, it can be helpful for advanced functionalities.

The Surefire Plugin is the default Maven plugin used to execute tests and generate reports. Configuring the Surefire Plugin explicitly inpom.xml is optional if we are using the default settings, as Maven will use the plugin's default settings.

If we do not specify the Surefire Plugin inpom.xml, Maven will use the default version bundled with the Maven installation to run the tests. This default configuration might not always be suitable, especially for JUnit 5.

<build>
    <plugins>
        <!-- Surefire Plugin for Unit Tests -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>3.0.0-M7</version>
            <configuration>
                <includes>
                    <include>**/*Tests.java</include>
                    <include>**/*Test.java</include>
                    <include>**/*Spec.java</include>
                </includes>
            </configuration>
        </plugin>
        
        <!-- Failsafe Plugin for Integration Tests -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-failsafe-plugin</artifactId>
            <version>3.0.0-M7</version>
            <executions>
                <execution>
                    <goals>
                        <goal>integration-test</goal>
                        <goal>verify</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <includes>
                    <include>**/*IT.java</include>
                    <include>**/*ITCase.java</include>
                </includes>
            </configuration>
        </plugin>
    </plugins>
</build>

Package org.junit.jupiter Details

Sub-package

org.junit.jupiter.api

org.junit.jupiter.engine

org.junit.jupiter.api.condition

Annotations

This package contains the core annotations and assertions for writing tests in JUnit Jupiter.

Test Annotations (org.junit.jupiter.api)

These annotations are used to define and configure tests.

• @Test: Marks a method as a test method.

• @RepeatedTest: Marks a method to be repeated a specified number of times.

• @TestFactory: Marks a method as a factory for dynamic tests.

• @TestTemplate: Marks a method as a template for tests to be invoked multiple times.

• @Disabled: Disables a test class or test method.

Lifecycle Annotations (org.junit.jupiter.api)

These annotations are used to define setup and teardown logic for tests.

• @BeforeEach: Indicates that the annotated method should be executed before each @Test method.

• @AfterEach: Indicates that the annotated method should be executed after each @Test method.

• @BeforeAll: Indicates that the annotated method should be executed before all @Test methods in the current class.

• @AfterAll: Indicates that the annotated method should be executed after all @Test methods in the current class.

Display and Tag Annotations (org.junit.jupiter.api)

These annotations are used for setting display names and tagging tests for selective execution.

• @DisplayName: Sets a custom display name for the test class or test method.

• @DisplayNameGeneration: Defines a custom display name generation strategy for test classes.

• @Tag: Declares tags for filtering tests.

Conditional Test Execution Annotations (org.junit.jupiter.api.condition)

These annotations are used to enable or disable tests based on certain conditions.

• @EnabledIf: Enables a test or container if the specified condition is met (used with a custom condition).

• @DisabledIf: Disables a test or container if the specified condition is met (used with a custom condition).

• @EnabledOnJre: Enables a test or container only on the specified Java runtime environments.

• @DisabledOnJre: Disables a test or container on the specified Java runtime environments.

• @EnabledOnOs: Enables a test or container only on the specified operating systems.

• @DisabledOnOs: Disables a test or container on the specified operating systems.

• @EnabledIfEnvironmentVariable: Enables a test or container if the specified environment variable is set to the specified value.

• @DisabledIfEnvironmentVariable: Disables a test or container if the specified environment variable is set to the specified value.

• @EnabledIfSystemProperty: Enables a test or container if the specified system property is set to the specified value.

• @DisabledIfSystemProperty: Disables a test or container if the specified system property is set to the specified value.

Timeout Annotations

These annotations are used to enforce timeouts on test execution.

• @Timeout: Fails a test if execution exceeds the specified duration.

Nested Test Annotations

These annotations are used to create nested test classes.

• @Nested: Denotes that the annotated class is a nested, non-static test class.

Extension Annotations

These annotations are used to register extensions to extend the behavior of tests.

• @ExtendWith: Registers extensions for the annotated test class or test method.

Parameterized Test Source Annotations

These annotations are used to provide sources of arguments for parameterized tests.

• @ValueSource: Provides a single array of values for a parameterized test.

• @EnumSource: Provides enum values for a parameterized test.

• @MethodSource: Provides values from a method for a parameterized test.

• @CsvSource: Provides CSV values for a parameterized test.

• @CsvFileSource: Provides CSV values from a file for a parameterized test.

• @ArgumentsSource: Specifies a custom ArgumentsProvider for a parameterized test.