title: Coverage.py not giving valid results
body: <p>I was hoping someone could explain how coverage.py works since after reading the documentation on it I am still rather confused.  I am attempting to figure out code coverage by a <code>TestCase</code> class and the results haven't been very logical, particularly since after commenting out large chunks of tests the percent missing remains the same. I am working in the community version of PyCharm and haven't been able to find any alternatives to coverage.py so if you could recomend another option that would be appreciated too.</p>