The above link got passed around at Guidewire the other day. It reminded me of the consulting days where we had to figure out the right answer for the right stage of the agile enablement.
This also reminded me about another interesting thing is this "90%, 50% rule" from Adam. He told me that he started paying more attention to the line coverage of the projects that he has been on. What he noticed is that the line coverages seem always end up at 90% or 50%. Normally 90% are the projects that developers are doing test-driven development, and 50% are the ones that people recognize that writing tests is an essential part of software development but not necessarily in the TDD fashion.
I do remember that all my projects in ThoughtWorks had the around 90% coverage. I wonder how much we have at Guidewire or my open source projects. The reason that I don't know is because at Guidewire the QA tests affects the coverage as well so it is not the same thing. My open source projects are all done in the TDD fashion so I never bothered to spend time create something that I don't really use.