title: Does python-xdist plugin causes pytest_generate_tests to execute multiple times?
body: <p>I have a simple test.</p>
  
  <pre><code>def test_sample(str):
      print str
  </code></pre>
  
  <p>And using pytest_generate_tests() e.g.</p>
  
  <pre><code>def pytest_generate_tests(metafunc):
      argnames = [str]
      argvalues = [[Hello], [World]]
      print "Entered pytest_generate_tests"
      metafunc.parametrize(argnames, argvalues)
  </code></pre>
  
  <p>Now if I use python-xdist to run tests in parallel. I see that pytest_generate_tests() is called "n" number of times depending upon the cmdline option.</p>
  
  <p>py.test -n 2 --> prints "Entered pytest_generate_tests" twice.
  Is this correct behavior ? I was expecting that only the test will be executed in separate thread. </p>
  
  <p>Env:
  python 2.7
  py.test 2.5.2
  pytest-xdist 1.10</p>