Black box (functional) testing is the way to go. I created a flow style of testing, which allows "Fast & Thorough Testing". This is a javascript & jasmine exten

Black box (functional) testing is the way to go. I created a flow style of testing, which allows "Fast & Thorough Testing". This is a javascript & jasmine extension, but the concept can be applied to other languages. http://briantakita.com/articles/fast-and-thorough-testing-with-jasmine-flow/ http://briantakita.com/articles/fast-and-thorough-testing-wi... The nice thing is the testing does not have a large effect on the implementation, so you have the freedom to change the implementation without the tests failing. The test suite scales since edge cases can be grouped together into a single flow. This removes extraneous runtime burden of having to recreate the same context for a each individual edge case. I find that I don't need to be performing TDD as often.