As much as I agree with @JanVladimirMostert, I also totally agree with the sentiments expressed by @lorthirk and @fibric.
Writing good code starts well before a single line of code is written. Environmental factors like the 'culture' under which people work (eg a culture that favours well understood code that can be defended to peers versus a culture that favours a non-thinking implementation of dictum from some 'architects' above) are likely to produce very different end results with 100% coverage. Test coverage can do only so much to mitigate against badly designed systems, cut-and-paste programmers or ones whose objective is to get something 'to work' without necessarily understanding why or how.
Testing is great, but writing good code in the first place and then testing is even better, I would argue.