Java Unit Testing with JUnit - Tutorial - How to Create And Use Unit Tests

Full tutorial on creating Unit Tests in Java with JUnit!
Do you write Java code that you're just not confident is 100% right? You can create unit tests using the JUnit testing framework to verify your Java code, and I'll show you exactly how to do it.
Many beginners don't know there's a great way to test their code with simple, fast tests and make sure their code is working exactly how they think it is.
The IntelliJ testing tools also make creating and running your Unit Tests super simple.
In this beginner's Java tutorial video, we'll do a full walkthrough of why and how you can create your own unit tests!
Learn or improve your Java by watching it being coded live!
Hi, I'm John! I'm a Lead Java Software Engineer and I've been in the programming industry for more than a decade. I love sharing what I've learned over the years in a way that's understandable for all levels of Java learners.
Let me know what else you'd like to see!
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[@Roberto-oz6et]

Your channel is pure GOLD! I'm learning more in a few minutes than an whole semester of classes.

[@jeromepincus8529]

So true

[@tejumania]

Honestly there's no better refresher course on java unit testing than this. Short, precise, keeps your gears turning and leaves you wanting to know more. Thank you so much John.

[@muhammadhassaanbasil8599]

Concise, Crisp & To-the-point. Short videos, really time saving. Great work John.

[@olillin]

I've been trying to learn unit testing for ages and this made everything so much clearer!

[@macmcleod1188]

These are all wonderful. I'm a retired Java 6 programmer writing Minecraft mods in Java 8, 16, and 17. Your videos are clear and concise! They help me a lot.

[@Chronozia]

Hey John! I took a course in the fundamentals of computer science last year where our professor mentioned the importance of unit testing and made us all write our own ones without really explaining the reason why or showing how to properly do it. This video really cleared that up for me. Thank you so much!

[@gplus46]

"run our test with coverage" was a requirement for project...Its clearer now. That was a treat. Great video

[@samueldnc]

You're brilliant! I'm a senior Java developer but I don't have these didactics and ease to explain/teach. Awesome job

[@Hurosaki_]

John, i almost said that this was the most easy topic i learned in java, but when i read other comments, i realized its because your teaching method is simply great. I’m glad i found you!

[@marmont8005]

Today, I crashed production because I didn't review and test my code. This was a valuable lesson for me. A colleague with more experience showed me how I could have detected this error through unit testing. We wrote 8 test cases within 20 minutes that could have assessed the functionality of my changes, and I would have noticed the bug. I am glad that we have an open culture for acknowledging errors, and that I was 'allowed' to make this mistake.

[@marmont8005]

I didn't realize how I had caused this error until we received emails from the company. In a mapper method, I used .filter(Objects::isNull) in a stream filter instead of .filter(Objects::nonNull). This led to the occurrence of the error on 6000 devices. It dawned on me that a slight oversight can impact hundreds to thousands of people. From now on, I will be more conscientious and refrain from putting my code into production until I am 100% sure that it performs its intended function.

[@JoeyCodes]

How are ya'll getting jobs out here not knowing how to test your code ;-;

[@xq510]

THIS IS AMAZING! I loved how you provided context and explained everything so clearly!!

[@DC-sp4sk]

Best video ever on JUnit by a long shot. Would really love to see more advanced videos on this topic!

[@raghavanaliassaravananm1546]

Thanks and kudos for the Coverage aspect in Intellij IDEA.

[@nipunlakshank]

This is the best beginner friendly unit testing tutorial I've found so far

[@amjadsaad9545]

I'm really thankful to you. I'm currently in the process of studying. And I researched it because my doctor didn't talk about it and I found a similarity between it and the Java language, but it's not a regular Java, it's a test for Java. Thank you. I really understand. And of course I'm proud of myself because I researched who you might laugh at. But that's true. Thank you again❤

[@Tolgasah]

Hi John, thanks for the video. I have to write my own unit tests for a project assignment, but have never done or got properly shown how to. This video cleared all my questions.

[@samueloverspelham2322]

As a Java developer, this channel has been very helpful to me in every way.. Thanks to you.

[@diegoruiz5265]

You are great John ! I really enjoy your videos, they are so practical but with a lot of useful information and knowledge. You do that complex topic looks really easy and funny. Keep with this awesome work. Thank you !

[@gabrieldenobrega]

Thank you for this video. It's clear that this video is just a summary of what unit tests are just like you said. However, only your video was able to really make me understand what unit testing in Java is about.

[@eduonnetcomputer8878]

I have been watching since a year. Your videos are very simple to understand. Thank you.

[@JLSXMK8]

A video on lambdas expressions would be so awesome, especially when the concept is partnered with runnable class instances. These together are the only way I know in java to make a responsive GUI application.

[@tarifadib]

thank you, i was able to create and test individual test cases with this video.

[@semilife]

John your videos are great, clear concise and informative.

[@lekhanh9085]

Thanks John, I understood the basics of JUnit test in Java through your easy to understand examples. 😊

[@TomAinsworth94]

Awesome vid John, thanks for going into so much detail in an actual use case!

[@Roshni1406]

Hey John Thank you so much for this video , you were just explain the basic unit testing in a simple way. This is a great video for beginners.👍

[@mrnoname2462]

Been exposed to introduction of JUnit today, lucky to have this lesson!

[@darsanas6741]

Thanks a lot John. I started loving Java after watching your videos! This topic was so interesting.

[@ajithak.s.5224]

Simple and precise illustration. Thank you John. Probably including parametrized junits supported in Junit5 would be better.

[@waffle8364]

The one testing framework I've ever loved and enjoyed was RSpec for Ruby or Rails. Extremely easy to setup, read and write tests.

[@iamhassell]

Great intro to unit testing John, awesome! Thanks!

[@gabrielv.4358]

That is insanely complicated, wow! So cool!

[@mahodaadikari4116]

Thanks John. Another crystal clear explanation. Straight to the point 👌 💯

[@alexanderanastasiadis9284]

Hi John , you are the reason who i love the Java. Every video is incredible understandable. Thanks a lot 😎

[@jhonysantosdesouza]

It's a wonderful video!! Many thanks John

[@Decent138]

i have not understands this topic in my class but now i am perfect with this topic.... Thank you professor

[@slai2389]

Thanks for your video sincerely. Every time I learn new things from you.

[@sunruiheng4255]

Awesome overview and introduction to JUnit, thanks!

[@illegalgiant_]

needed a refresher as i apply to sdet jobs. excellent clear stuff. thanks.

[@animeshsrivastavash]

Another great video John! Looking forward to the jvm memory management video; if possible please give it a shot ...

[@umiskan5819]

Great explanation! Great work! Simple and to the point Thank you!

[@brenodelgado1128]

Hey John, congrats for your content. It's really clarefull and understood. Thanks from Brazil, let's keep coding.

[@Wow-uj3uj]

This video has made me subscribe. So well spoken and well communicated I had no choice! Thank you for this very informative video

[@ndk8111]

Thanks John. Finished your lecture then went to try to implement a few of the junit5 test methods for the very first time. Your explanation was very good. One thing I wished you touched was how to resolve dependencies needed to run junit5. I grabbed one of the dependencies in mvn repository Jupiter-engine and that seemed sufficed to resolve my missing assertTrue(). These small things very briefly but ought to be covered In your demos I think.

[@HR-pz7ts]

Amazing as always John!

[@anjananisal2672]

Crystal clear explanation, thank you!!

[@lucasalledi]

going through your classes while taking part in a bootcamp. really appreciate your help!

[@CodingWithJohn]

Glad it's helping!

[@dipalisavaliya295]

very nicely explained in short time and covered very good scenarios!! Thanks for your efforts :)

[@sirfranciscanadianbacon1468]

That was so well described. Very very helpful. Your videos are also produced very well.

[@user-ie9yw4wr2j]

Thanks!!! Eezy tutorial on unit testing

[@jaaeamor7901]

Awesome video! Thanks for posting!

[@ribamiltombezerradelima3483]

Wow! Thank you so much! Your video is really helpful and engaging! Keep it up,pal!

[@oleksiil.9892]

Very cool stuff for a java beginner like myself )) thank you!

[@regatonic]

That was excellent, love your tutorials!

[@milenatenorio2506]

Thank you very much for the video! The teaching and English are perfect for people who do not speak English as a native language.

[@matiasmoresi5040]

Beautifully explained! Thank you very much!

[@igorkulishov8285]

Awesome! Thank you so much! Great explanation.

[@jp77355]

TY!, the exception part was the best in the video!

[@michael_scarn_]

Thank you John, much appreciated!❤

[@2002egncn]

Very well explained! Thank you.

[@k.k9206]

That was awesome john! great explanation! Thank you so much.

[@prashanthdp9501]

Very organised and very well explained, Thank you!

[@ShaneHajankangson]

Nice work! Really informative video and easy to follow along on

[@beetc305shivsundarbankar9]

Hit the like, if you have been watching many tutorials and finally, you get the proper context with clear explanations.

[@saiashok28]

Really good teaching. Thanks for sharing this video.

[@vivzyw]

This video is amazing! Thank you so much for sharing!

[@K4ziq]

Hey John! Thanks for your hard work! You do great job with this short explanatory videos! Create one with lambda expression please! :)

[@juancarloscardona5613]

Thanks for this video! I recently joined my first hackathon and I was looking forward to using unit testing in Java for the first time, you explained it very well and it was easy to understand. Nice work :)

[@carloschacon5951]

MinTIC???

[@lonesareer]

Hey John, Thanks for your great work. Your content and explaination is exemplary

[@whitneythung2792]

This is an awesome tutorial on how to write JUnit Tests. You explained this so well for a slow learner like me. Thanks for the help!

[@CodingWithJohn]

Glad it was helpful!

[@mohamed-alimessedi3]

Thank you very much for sharing this in such a clear way.

[@rollingdice]

thanks John, I learned some new info from this lesson

[@henryicruise860]

I've always been scared of Testing, thanks to this video, I feel quite comfortable with it now.

[@my_video_collection]

now 2:23 am, but I'm sitting and watching you. It's so cool. Firstly I'm learning Java, secondly I'm improving my English (at least listening)😍

[@micleh]

I enjoyed the topic of the video, since unit tests are not necessarily what you have to do at school (and it's not in the curriculum). What I also liked was you switching to IntelliJ. I've been experimenting with my students, and we tested 3 different IDEs. They said that they felt most comfortable with IntelliJ and also appreciated the helpful tips that guided them towards fixing errors. I'd also like to give you props for the way you present the topics, among them being voice, intonation, gestures and pace.

[@noobster9212]

Truth to be told, curriculum for computer science in most university is outdated. Most lecturers stopped learning new things whereas the cs world is evolving every second.

[@ngndnd]

im taking a junit class rn and its a complete joke of a class.

[@albertbokor6643]

We actually have a course that goes all in on these features. It feels a bit awkward to do this much stuff for a conceptually small assignemt project but still something practically useful.

[@gabrielv.4358]

so true. intellij is the better of them all, and its free

[@simonandris4730]

That was very informative . Thanks for sharing your knowledge with us

[@mastershonobi110]

Very noice!!! As a “beginner” learning on my own these lectures are important lessons. Great Intro exposure to thinking about writing code holistically. Ty. 🙌🏿🙏🏾

[@mohamedibrahim-qm1cr]

we should be friends lol i'm also just started Java! maybe CodingMates?

[@mastershonobi110]

@@mohamedibrahim-qm1cr where are you in your journey? Are you taking a course? With who? Asking for potential friend. Lol

[@mohamedibrahim-qm1cr]

@@mastershonobi110 just in java for a week now, I'm in a bootcamp plus resource from Plural Sight.

[@theblindprogrammer]

Yes, John's instructions are clear and to the point.

[@theblindprogrammer]

@@mohamedibrahim-qm1cr Which level are you in? Did you reach objects and inheritance?

[@soumikbanerjee3059]

Thanks. Got a clear understanding.

[@nyizeya99]

Your contents are really helping

[@tarikuasfaw6405]

Wow I pretty much appreciate you John I am so happy to get your channel

[@peanuthead32]

this was just amazing. very well explained.

[@dev_project2012]

very good explanation , I will use more and more unit test

[@joaopaulocorreaparise5126]

Love your content! Keep on, John!

[@DavidVCastro]

Amazing how much you covered in 21 minutes!

[@bbaekkhyyunne_4750]

very clear with thinking procedures

[@OkLittleBuddyCalmDown]

Thanks for making current and superior Java videos

[@janfelixvs]

Great video, you helped me a lot!

[@shaharts8333]

Good starter video for unit testing

[@kemiles]

Appreciate you and this channel ... would love to see you cover mockito!

[@harshachakraborty3505]

Hi John, Thanks for all these videos. Please make a video on concepts of functional interface and lambda expression.

[@rrroman870]

Thanks so much for the tutorial. It helps a lot!

[@FukSN]

Nice tutorial and well explained as usual. Thank you

[@brahmareddydareddy2110]

This is so nice and wonderful way of teaching

[@natashasthilaire1950]

This video was amazing, thank you!!!

[@melbali7828]

John you are the best of the best. Keep it up and would like to see some Spring boot tutorials. Many Thanks

[@samuvisser]

Long time programmer but never wrote a single unit test. Its this thing i know i should do, but I seriously never have time for. This video is a actually a great example, ur unit tests tend to use as much or even more lines of code than the original. In the real word the next deadline is always yesterday…

[@vinaypawde9894]

Hi John.love your videos..you explain both concepts and code very clearly..could you please do a video around stack/queues and bfs/dfs algos? Thanks a lot :)

[@user-pb6ps2mb4y]

John! Thanks a lot!!!! Your video was super duper helpful! Really simple and clear for a novice!!! Like and subscription!

[@yogeshdharya3857]

Had an assignmen to perform unit testing in Java usign the Junit . Was recommended to watch this video of yours . Your doing a great job ceating content for beginners like me Sir John . Had to subscribe ! Keep up the good and humble work !😇

[@CodingWithJohn]

Awesome, I'm glad it helped! And thankful to whomever recommended it!

[@Andorkien]

Great video John, thanks!