A unit test is a way of testing a unit - the smallest piece of code that can be logically isolated in a system. In most programming languages, that is a function, a subroutine, a method or property. The isolated part of the definition is important.

It is a way to automatically test if the output of your code is the expected one.

Why and What Unit Testing

Now you think: Why should I set up a Unit Test. It's extra effort and besides I can just press play and test it?

There are many advantages to Unit testing.

• Allows you to test parts of the code that might not be playable for some reason.
• Allows you to test the functions in a void, meaning that:
• In a chain of functions you can easily find where the problem lies.
• You do not depend on other functions.
• Once set up you can quickly test with different inputs.

This does not mean that you stop testing your work in-game.

Now you think: What should I test, everything?

This is a difficult question.

There are thing that you should test, that you shouldn't test and things you cannot test. The best thing you can do is think critically and experiment yourself.

Unit Testing in Unity

Unity has it's own libraries and tools to help set up all the tests you need. For more info Click Here

Also here's a video: