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

## Creating our first JUnit test

We usually use test classes to interact with JUnit 5.

We usually use test classes to interact with JUnit 5. Let’s get a deeper understanding of a test class.








package io.educative.junit5;


import org.junit.jupiter.api.Test;

class FirstTest {

    @Test
    void firstTest() {
        System.out.println("First Test");
    }
}



## Characteristics of a test class

A test class has the following characteristics:
- In JUnit 4, it’s mandatory that all test classes and methods have public access. In JUnit 5, this restriction is relaxed because the framework uses reflection to discover the test classes and methods. We should have **default access**.
- Java creates a **no-argument constructor** implicitly for each class.
- It should have at least one **test method**.

## Characteristics of a test method

A test method has the following characteristics:

- It should have the `org.junit.jupiter.api.Test` annotation.
- It should return `void`.
- It should have parameters.

>Note: We’ll cover parameters in detail in the upcoming lessons.

## Naming your tests using @DisplayName

Developer Phil Karlton said, “There are only two hard things in Computer Science: cache invalidation and naming things.” 
Creating meaningful names for methods can be tough. To counter this problem, JUnit 5 allows us to assign appropriate names to the tests using  `@DisplayName`.

We add some descriptive text inside the `@DisplayName` annotation, like “Our First Test.”

# Creating our first JUnit test

We usually use test classes to interact with JUnit 5.

We usually use test classes to interact with JUnit 5. Let’s get a deeper understanding of a test class.








# Characteristics of a test class

A test class has the following characteristics:
- In JUnit 4, it’s mandatory that all test classes and methods have public access. In JUnit 5, this restriction is relaxed because the framework uses reflection to discover the test classes and methods. We should have **default access**.
- Java creates a **no-argument constructor** implicitly for each class.
- It should have at least one **test method**.

# Characteristics of a test method

A test method has the following characteristics:

- It should have the `org.junit.jupiter.api.Test` annotation.
- It should return `void`.
- It should have parameters.

>Note: We’ll cover parameters in detail in the upcoming lessons.

# Naming your tests using @DisplayName

Developer Phil Karlton said, “There are only two hard things in Computer Science: cache invalidation and naming things.” 
Creating meaningful names for methods can be tough. To counter this problem, JUnit 5 allows us to assign appropriate names to the tests using  `@DisplayName`.

We add some descriptive text inside the `@DisplayName` annotation, like “Our First Test.”

Learn to create unit tests with JUnit 5, and learn the characteristics of a test class and method.

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

Our First Unit Test with JUnit 5

Creating our first JUnit test

Characteristics of a test class