What is Unit Testing?
In simple terms, unit testing is a definition of tests to run on your code. Usually, these tests are automated. The "unit" in unit testing means that the tests should test the smallest functional units, like functions or methods. However, unit testing does not have to be limited to only testing small parts; it can also test interactions between parts with complex combinations and variables, and even test some visual elements, like whether or not a certain image is actually shown or if a class was applied to an XHTML tag.