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.

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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

## Introduction

The main difference between the previous versions of JUnit and JUnit 5 is the architecture.

In the previous JUnit versions, all the functions of the software were embedded into a single JAR file. This caused everyone to use the same JAR file regardless of the use case. For example, some developers may want to use JUnit to write unit tests, while others want to use it to develop build tools—both use the same JAR file. Similarly, frameworks and integrated development environments (IDEs) also used the same JAR File.

One group wanted to use the framework to write unit tests and the other wanted to support JUnit from their IDE (IntelliJ or Eclipse) or Build Tool (Maven or Gradle).

With the popularity of JUnit, almost all the famous build tools and IDEs started using JUnit.There was no separate **application programming interface** (API) created for them. Therefore, it created a coupling between the build tools, IDEs, and the JUnit Internals. Due to this, even a small change to JUnit’s internal API caused breaking changes in the build tools and IDEs.

One of JUnit’s developers, Johannes Link, states: 


> "The success of JUnit as a platform prevents the development of JUnit as a test tool ."

This was the driving point behind the architectural change of JUnit.






# Introduction

The main difference between the previous versions of JUnit and JUnit 5 is the architecture.

In the previous JUnit versions, all the functions of the software were embedded into a single JAR file. This caused everyone to use the same JAR file regardless of the use case. For example, some developers may want to use JUnit to write unit tests, while others want to use it to develop build tools—both use the same JAR file. Similarly, frameworks and integrated development environments (IDEs) also used the same JAR File.

One group wanted to use the framework to write unit tests and the other wanted to support JUnit from their IDE (IntelliJ or Eclipse) or Build Tool (Maven or Gradle).

With the popularity of JUnit, almost all the famous build tools and IDEs started using JUnit.There was no separate **application programming interface** (API) created for them. Therefore, it created a coupling between the build tools, IDEs, and the JUnit Internals. Due to this, even a small change to JUnit’s internal API caused breaking changes in the build tools and IDEs.

One of JUnit’s developers, Johannes Link, states: 


> "The success of JUnit as a platform prevents the development of JUnit as a test tool ."

This was the driving point behind the architectural change of JUnit.






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

JUnit 5 Architecture

Introduction