Derick Bailey has a good post about determining the cost vs. value of doing testing. No one who’s read this blog will be surprised that I particularly like this:
“There is a cost associated with a test-first approach. If you put in 100% unit test coverage, and 100% integration test cover and 100% end-to-end functionality test coverage, then you end up with 300% coverage of your system. Is the cost of maintaining 300% coverage worth it in your system? “
It’s a good read, check it out.