title: How to pass complex class members to pytest parametrize decorator
body: <p>I need to pass class members as parameters to <code>pytest.mark.parametrize</code>.
  The following code does not work (I've used simple members strings, but in my case they are complex and constructed):</p>
  
  <pre><code>import pytest
  class TestSmth(object):
       def setup_class(cls):
           cls.a = "a"
           cls.b = "b"
           cls.c = "c"
  
       @pytest.mark.parametrize("test_input,expected", [
       (self.a, "a"),
       (self.b, "b"),
       (self.c, "c")
       ])
       def test_members(test_input, expected):
           assert test_input == expected
  </code></pre>
  
  <p>Is it possible to achieve such result?
  Or something similar?</p>