title: py.test skips test class if constructor is defined
body: <p>I have following unittest code running via py.test.
  Mere presence of the constructor make the entire class skip when running
  py.test -v -s</p>
  
  <p>collected 0 items / 1 skipped</p>
  
  <p>Can anyone please explain to me this behaviour of py.test?</p>
  
  <p>I am interested in understanding py.test behaviour, I know the constructor is not needed.</p>
  
  <p>Thanks,
  Zdenek</p>
  
  <pre><code>class TestClassName(object):
      def __init__(self):
         pass
  
      def setup_method(self, method):
         print "setup_method called"
  
      def teardown_method(self, method):
         print "teardown_method called"
  
      def test_a(self):
         print "test_a called"
         assert 1 == 1
  
      def test_b(self):
         print "test_b called"
         assert 1 == 1
  </code></pre>