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How to Learn Unit Testing in Java: JUnit and Mockito Courses

by Javin PaulAugust 29th, 2019

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JUnit and Mockito are two of the most popular testing libraries for Java applications. JUnit is the defacto standard for unit testing in Java, but you often need Mockito, a mocking framework that is often used along with JUnit to make unit testing easier. In today’s world of DevOps and Automation, there is increased focus on code reviews and unit testing, and you just can’t get away with not writing tests. Every good software developer must know how to write unit tests, and nearly all Java jobs ask for testing skills.

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Hello guys, today I am going to talk about JUnit and unit testing, one of the key skills for any software developer. You may already know that JUnit and Mockito are two of the most popular testing libraries for Java applications, and you will find them in almost every Java application classpath.

I often meet and work with Java developers who know Java well but haven’t written a single unit test. When I ask them why don’t you write unit tests, they come up with many excuses like they don’t have time for writing unit tests, there is always deadline pressure, and some of the honest guys will tell you that they tried writing but give-up after 10–15 minutes due to difficulty in testing their code.

Whatever your reason for not writing a unit test, I don’t think it’s going to work anymore because, in today’s world of DevOps and Automation, there is increased focus on code reviews, unit testing, and integration testing, and you just can’t get away with not writing tests.

In fact, every good software developer must know how to write unit tests, and nearly all Java jobs ask for unit testing skills, and those who don’t mention it assume that you already know unit testing.

Unit tests are at the lowest level and typically check a single method to confirm that they return the correct result.

Don’t worry if you haven’t written any unit tests. As long as you can accept the fact, and you are willing to learn unit testing in Java using JUnit and Mockito, you are in good shape.

In the past, I have shared some great books for learning unit testing in Java like the Test-Driven and JUnit in Action, and today, I am going to share some of the online courses you can use to learn JUnit 5 or Jupiter, the latest version of JUnit library, and Mockito to write a unit test for your Java application.

You can use these online courses to get up-to-speed with JUnit and Mockito. This will not only help you in your current project but also increase your chances of getting a job with better pay. Believe me, everyone loves a good software developer and there is always a demand for a programmer who can code and write good tests.

What Is Unit Testing and Why Do We Write Unit Tests?

If you are thinking about why you should write unit tests, shouldn’t we get paid for writing code that adds functionality? Then let me tell you that unit tests are necessary for every good piece of software and every programmer should write a unit test.

It increases confidence during development and helps you to write cleaner, more reusable code, and it also helps you catch bugs earlier.

Catching mistakes in the development phase is a lot less costly than finding them in production. It not only saves you from embarrassment, but it also saves your company and user from frustration.

Now that you are convinced you to want to learn unit testing, you can explore these online courses to get started!

Top 5 Online Courses to Learn JUnit in-depth

In Java, JUnit is the defacto standard for unit testing, but you often need Mockito, a mocking framework that is often used along with JUnit to make unit testing easier.

I have been using JUnit since JUnit 3, which was prior to annotations. Then JUnit 4 comes in 2006, and after 11 years of waiting, JUnit 5 came out in September 2017.

As of writing, this is the latest version of JUnit and every Java developer should learn it. Even though a lot of projects are still using JUnit 4, learning JUnit 5 will help you write better tests faster by leveraging new features.

Most of these courses cover JUnit 5, but I have also included a course on test-driven development to learn some of the best practices and techniques for improving unit tests.

1. Java Unit Tests for Beginners

This is one of the best courses for learning how to write Java unit tests with JUnit 5 or Jupiter. This course is ideal for all kinds of Java developers — from intermediate developers with several years of experience to beginners who have not written a single unit test before.

The course is full of practical examples, additional exercises, and a unit testing cheat sheet. It starts from scratch, telling you what a unit test is and why you should use it, then teaching you how to do it step by step.

Learn more: Java Unit Tests for Beginners: JUnit 5 for your first IT job

The course also teaches you unit testing best practices, and their sample project, The HealthyCoder example, makes things really interesting. The course is filled with exercises and an extra JUnit cheatsheet that provides enough knowledge to start writing unit tests on your own.

On top of all of this, instructor, Adrian Więch has an excellent voice, which is just perfect for teaching, and his voice modulation, pace, and skill make things simpler, which makes this course very interesting. I strongly recommend this course to all Java developers who want to learn unit testing this year.

2. Learn Unit Testing With JUnit and Mockito in 30 Steps

This is another awesome course to learn Mockito and JUnit — the most popular unit testing and mocking frameworks in the Java world — with 25 examples.

I am a big fan of Ranga and his in28-Minutes courses; he typically focuses on 20 percent of the important stuff that is used 80 percent of the time. Having seen his Spring Masterclass and Microservices course, I know that this will also be the good one and it didn’t disappoint me.

Learn Mockito and JUnit (Unit Testing in 30 Easy Steps

The course takes a step-by-step approach, and in 30 steps, it will teach you all you need to know about Mockito and JUnit so you can write your own tests. The first 18 steps are about Mockito and the last 12 are about JUnit.

The course not only covers basic stuff, like writing simple tests, but also covers more advanced concepts like testing static methods, organize JUnit tests into suites, parameterized tests, testing exceptions in JUnit tests, and, in general, how to write better tests.

Overall, this course provides a good, hands-on, brief course for learning Mockito and JUnit in less than 5 hours total.

3. Java Unit Testing With JUnit 5

I recently come across this new online platform for learning. It’s a bit different from Udemy and Pluralsight because it’s interactive and allows you to run code right from the webpage, which makes it very effective.

Like the previous two courses, this course will also teach you how to write unit tests with JUnit 5, but it also covers topics like why unit tests are important and structure of good unit tests, assertions, assumptions and parameterized tests, and more.

If you like interactive learning, then you can check out this course; it comes with three free previous lessons and a 30-day return policy, which is good enough to give it a go.

Learn more: Java Unit Testing with JUnit 5

4. Practical Test-Driven Development for Java Programmers

Learning JUnit is one thing, but writing unit tests is another. It’s easy to write a trivial unit test for a sample project, but when you go into a real project where TDD has not been used and no unit test is written, you will find a lot of challenges when writing your very first test — that’s where this course comes in handy.

Practical Test Driven Development for Java Programmers
Course Ratings are calculated from individual students' ratings and a variety of other signals, like age of rating

I have purposefully included this course because I believe learning TDD and unit testing, in general, is as important as learning JUnit and Mockito.

The instructor Matt Greencroft is very experienced and will teach you how to write unit tests for trickier scenarios and show you use TDD techniques to fix applications that weren’t developed using TDD.

My favorite part of this course is Chapter 10: Handling Legacy Code because this is something a Java developer needs to do in his day-to-day coding. I have learned a lot of good stuff from this course and feel I know unit testing better than before.

Therefore, I highly recommend this course for all Java developers who want to learn unit testing or improve their TDD skills, btw, if you need books you can also read my list of JUnit and TDD books for Java Programmers.

5. Test-Driven Development Practices in Java

This is another course I have included on Test-Driven Development (TDD) practices and tools supporting TDD on the Java platform, including JUnit and Mockito.

It nicely complements the previous course and covers things that are not covered in theirs, like PowerMock and DBUnit.

Test-Driven Development Practices in Java
Overview of Practices, Principles, and Tools Hello. This is Mike Nolan, and welcome to this Pluralsight course

Instructor Mike is a solution architect for US Foods and worked in IT for over 15 years, holding roles focused on technical leadership, solution architecture, and enterprise architecture, which means you will learn a lot from his experience.

Though, you would need a Pluralsight membership to access this course, which cost around $29 per month or $299 per year. It may seem costly, but to be honest with you, it’s completely worth it, as it gives you access to 5000+ online courses on Pluralsight and numerous quizzes and exercises to learn anything you want.

Anyway, even if you don’t have a membership, you can still get access to this course by using their 10-day FREE pass, which allows 200 minutes of access and is enough to complete this course.

That’s all for now on some of the best courses for learning Mockito and JUnit. I have told my readers to learn unit testing for a long time. I had included this as the first thing on my list of 10 things Java programmer should learn and also shared some free courses to learn JUnit earlier. If you don’t have any goals for 2019, make unit testing your top priority this year.

10 Things Java Programmers should learn in 2019

It’s also worth noting that JUnit 5 tests will run with Java 8 or above, so it’s also good to learn Java 8 if you haven’t. Always remember: Writing better unit tests distinguish great programmers from average programmers!

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Thanks a lot for reading! If you like these JUnit 5 online courses, then please share them with your friends and colleagues. If you have any questions or feedback, or you want another course to add in this list, feel free to drop a note. All the best with your unit testing journey!