
A sesssion-fixture which can look at all collected tests
********************************************************

A session-scoped fixture effectively has access to all collected test
items.  Here is an example of a fixture function which walks all
collected tests and looks if their test class defines a "callme"
method and calls it:

   # content of conftest.py

   import pytest

   @pytest.fixture(scope="session", autouse=True)
   def callattr_ahead_of_alltests(request):
       print "callattr_ahead_of_alltests called"
       seen = set([None])
       session = request.node
       for item in session.items:
           cls = item.getparent(pytest.Class)
           if cls not in seen:
               if hasattr(cls.obj, "callme"):
                  cls.obj.callme()
               seen.add(cls)

test classes may now define a "callme" method which will be called
ahead of running any tests:

   # content of test_module.py

   class TestHello:
       @classmethod
       def callme(cls):
           print "callme called!"

       def test_method1(self):
           print "test_method1 called"

       def test_method2(self):
           print "test_method1 called"

   class TestOther:
       @classmethod
       def callme(cls):
           print "callme other called"
       def test_other(self):
           print "test other"

   # works with unittest as well ...
   import unittest

   class SomeTest(unittest.TestCase):
       @classmethod
       def callme(self):
           print "SomeTest callme called"

       def test_unit1(self):
           print "test_unit1 method called"

If you run this without output capturing:

   $ py.test -q -s test_module.py
   ....
   callattr_ahead_of_alltests called
   callme called!
   callme other called
   SomeTest callme called
   test_method1 called
   test_method1 called
   test other
   test_unit1 method called
