title: Conditionally continuing with Python unit tests
body: <p>I have a test rig with three sets of tests for a sudoku solver:</p>
  
  <ol>
  <li>Test most functions individually</li>
  <li>Test the final few functions, which use those in step 1</li>
  <li>Test the final few functions with 95 harder puzzles</li>
  </ol>
  
  <p>As step 3 takes a while, I'm looking for a way to only go to the next step if all the previous steps passed. Is it possible to do this using the unit test framework, or is it easier to write my own control structure?</p>