Junit

JUnit is a simple framework to write repeatable tests. It is an instance of the xUnit architecture for unit testing frameworks.

The simplest way is as an expression in a debugger. You can change debug expressions without recompiling, and you can wait to decide what to write until you have seen the running objects. You can also write test expressions as statements which print to the standard output stream. Both styles of tests are limited because they require human judgment to analyze their results