History & Origin of Unit Testing In 1997, a programmer named Kent Beck created a development environment plugin, JUnit, to test small pieces of code. Developers wrote test code that assessed the source code. He called the approach unit testing. A unit test is a way of testing a unit – the smallest piece of code that can be logically separated into a system. In most programming languages, this is a function, a subroutine, a method, or a property. The