I&#x27;d definitely say that the absence of coverage is a problem.  My view is that coverage is necessary but not sufficient for good testing.<p>We talked a bit about classifying tests but didn&#x27;t do it in the end because it&#x27;s surprisingly hard to do.  I do know of one paper that looked at different kinds of tests, called &quot;The Effect of Code Coverage on Fault Detection under
Different Testing Profiles&quot;: <a href="http:&#x2F;&#x2F;goo.gl&#x2F;nnxgwE" rel="nofollow">http:&#x2F;&#x2F;goo.gl&#x2F;nnxgwE</a>.  The authors found differences between tests for error cases vs. tests for normal operation and between functional tests vs. random tests.  IIRC, they had undergrads do a term project that had to pass 1200 tests before the final submission, and the professors themselves wrote the tests, so categorization was a bit easier.