Unit testing is the most efficient way to detect as many errors as possible.
To perform unit testing, you pull one class, method, or function out of your application and test it by itself. The main advantage to unit testing is that it puts you much closer to the errors in a particular piece of code, thereby making error detection quicker and easier. White-box testing tests the construction of your code using data derived from the internal structure of a class, method or function. You can replay the test cases each time you modify your code. As soon as you have corrected all problems, you can safely check your code into the code repository.