Gain insights into unit testing with JUnit 5. Learn about assertions, assumptions, nested and parameterized tests, advanced JUnit 5 concepts, and integrating tests with Maven and Gradle.

Unit Testing Java Applications using JUnit 5_468 x 60 copy.png

junit5.tar.gz

mvn clean test

Unit Testing is a basic and essential skill to learn for any developer. In this course, you will learn what unit tests are, why they are important, and how to test your Java applications using the JUnit 5 Framework —  the most popular unit testing framework in the market for Java developers.

You will start with the fundamentals of Unit Testing and JUnit 5 and then gradually you will dive deep into the core concepts like assertions, assumptions, different types of tests like nested tests, parameterized tests, repeated tests, and more.

You will also learn some advanced concepts of JUnit 5 like the JUnit 5 extension model, dependency injection, how to migrate existing unit tests from JUnit 4 to JUnit 5, and how to integrate your unit tests with Maven and Gradle.

Unit Testing Java Applications using JUnit 5


If we add all the previous tests into one class, we can make a singular test class. The code below shows all the possible conditional execution annotations. It contains 11 tests.



import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.condition.*;

class ConditionalExecutionTests {
    @Test
    @DisplayName("Run the tests only on Linux and MAC OS")
    @EnabledOnOs({OS.LINUX, OS.MAC})
    void shouldRunTestsOnlyOnLinuxAndMACOS() {
        // Some Test Code
    }

    @Test
    @DisplayName("Should not Run on Windows OS")
    @DisabledOnOs(OS.WINDOWS)
    void shouldNotRunOnWindowsOS() {
        // Some Test Code
    }

    @Test
    @DisplayName("Should Run on Windows OS")
    @EnabledOnOs(OS.WINDOWS)
    void shouldRunOnWindowsOS() {
        // Some Test Code
    }

    @Test
    @DisplayName("Should Run only on JRE 17")
    @EnabledOnJre(JRE.JAVA_17)
    void shouldRunOnJre17() {
        // Some Test Code
    }

    @Test
    @DisplayName("Should Run on Java version from 8 to 17")
    @EnabledForJreRange(min = JRE.JAVA_8, max = JRE.JAVA_17)
    void shouldRunOnJreFrom8to17() {
        // Some Test Code
    }

    @Test
    @DisplayName("Should Not Run on JRE 16")
    @DisabledOnJre(JRE.JAVA_16)
    void shouldNotRunOnJRE16() {
        // Some Test Code
    }

    @Test
    @DisplayName("Should Run on Java version from 8 to 15")
    @DisabledForJreRange(min = JRE.JAVA_8, max = JRE.JAVA_15)
    void shouldNotRunOnJreFrom8to15() {
        // Some Test Code
    }


    @Test
    @DisplayName("Should Run on 64 Bit Architecture")
    @EnabledIfSystemProperty(named = "os.arch", matches = ".*64.*")
    void enableOn64BitMachines() {
        // Some Test Code
    }

    @Test
    @DisplayName("Should Run on 64 Bit Architecture")
    @DisabledIfSystemProperty(named = "os.arch", matches = ".*64.*")
    void disableOn64BitMachines() {
        // Some Test Code
    }

    @Test
    @DisplayName("Run Test if Custom Condition Matches")
    @EnabledIf("customCondition")
    void runTestIfCustomConditionMatches() {
        // Some Test Code
    }

    @Test
    @DisplayName("Do Not Run Test if Custom Condition Matches")
    @DisabledIf("customCondition")
    void doNorunTestIfCustomConditionMatches() {
        // Some Test Code
    }

    boolean customCondition() {
        return true;
    }
}


Complications occur when a project grows bigger. It’s easy to lose track of the number of tests inside a test class. We use nested tests to counter this.

# Understanding `@Nested` annotation

JUnit 5 provides the nested test functionality to group several tests into a single `Nested` test class.
It provides a `@Nested` annotation that we can use on top of the classes.
`Nested` tests are similar to nested classes in Java. They facilitate a hierarchical test structure.


# Code example

Understand nested tests are and their usage.

Before We Begin

Introduction to JUnit 5

Junit 5 Core Concepts

Dynamic Tests

Dependency Injection in JUnit 5

JUnit 5 Extensions

Migrating from Junit 4 to Junit 5

Appendix

BONUS: Useful Assertion Libraries

Conclusion

Nested Tests