"You might have a zillion unit tests that cause that line to be counted as covered, but still be missing the test that reveals the error case." Ironically it's

"You might have a zillion unit tests that cause that line to be counted as covered, but still be missing the test that reveals the error case." Ironically it's actually easiest to have 100% coverage in worse code, because the more entangled and coupled your code is, the more likely you are to hit branches that are not under test.