title: Is it possible exclude test directories from coverage.py reports?
body: <p>I'm kind of a rookie with python unit testing, and particularly coverage.py.  Is it desirable to have coverage reports include the coverage of your actual test files?</p>
  
  <p>Here's a screenshot of my <a href="http://kylefox-awesome-stuff.s3.amazonaws.com/coverage.png" rel="noreferrer">HTML report</a> as an example.</p>
  
  <p>You can see that the report includes <code>tests/test_credit_card</code>.  At first I was trying to omit the <code>tests/</code> directory from the reports, like so:</p>
  
  <pre><code>coverage html --omit=tests/ -d tests/coverage
  </code></pre>
  
  <p>I tried several variations of that command but I could <em>not</em> for the life of me get the tests/ excluded.  After accepting defeat, I began to wonder if maybe the test files are <em>supposed</em> to be included in the report.</p>
  
  <p>Can anyone shed some light on this?  </p>