title: Where do the Python unit tests go?
body: <p>If you're writing a library, or an app, where do the unit test files go?  </p>
  
  <p>It's nice to separate the test files from the main app code, but it's awkward to put them into a "tests" subdirectory inside of the app root directory, because it makes it harder to import the modules that you'll be testing.  </p>
  
  <p>Is there a best practice here?</p>