I don't agree with him.<p>Everyone knows when you are forced to write tests you code differently because you have to make the lines tested visible to the testing code. In legacy code without tests no one bothered to do this, which is why adding tests to legacy code is near impossible.<p>If 100% test coverage isn't forced you end up with lines that aren't visible to unit tests without re-factoring. If a bug is found in those lines and you want to add a test to demonstrate the bug has been fixed, you can't just make a minimal change - you have to re-factor the bloody thing, increasing the odds you will introduce another bug.<p>The bottom line is ensuring you have 100% test coverage (or even better 100% branch coverage) brings it's own rewards because of the discipline it enforces in code structure, and that is true even if those test lines don't do much in the way of useful testing.<p>So for me his argument only works you have 100% coverage. Thereafter, yeah, each test has to earn it keep.