As highlighted in the article, if you're using TDD, I'd almost argue setting coverage is redundant. It's nice as an enforcement mechanism, but TDD is going to have you at or near 100% coverage anyway.
The moral here is that while you may be leveraging TDD like a rockstar, you may have other peers on your project who are not and will do silly things just to hit the 100% goal.
I personally feel coverage works best as a metric. It should stay consistent or be on the upswing. A little dip here and there is perfectly acceptable, but a consistent drop would warrant some investigation.
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