title: Py.test: parametrize test cases from classes
body: <p>I'm currently following this <a href="https://pytest.org/latest/parametrize.html" rel="noreferrer">py.test</a> example and it works out when I do not use classes, however when I introduce test cases into classes I am failing.</p>
  
  <p>The smallest case I managed to write is the following:</p>
  
  <pre><code>import unittest
  
  import pytest
  
  class FixtureTestCase(unittest.TestCase):
  
      @pytest.mark.parametrize("test_input,expected", [
      ("3+5", 8),
      ("2+4", 6),
      ("6*9", 42),
      ])
      def test_1(self, a, b):
          self.assertEqual(a, b)
  </code></pre>
  
  <p>unfortunately when I execute </p>
  
  <pre><code>  py.test  test_suite.py
  </code></pre>
  
  <p>I get the error message:</p>
  
  <pre><code>  TypeError: test_1() takes exactly 3 arguments (1 given)
  </code></pre>
  
  <p>How can I do in order to generate a battery of test_1 tests?</p>