title: Only run setUp when a specific test requires it
body: <p>How would I limit running a setUp method to only run when a specific test is run, e.g.</p>
  <pre><code>class Tests(unittest.TestCase):
      
      setUpClass(cls):
          #requirements for all tests
  
      def test1(self):
          #something
  
      def test2(self):
          #something else
  
      def setUp(self):
          #requirements for test 3
  
      def test3(self):
          #something requiring setup
  </code></pre>
  <p>In this case, I only want to run setUp when test3 is called</p>