Detect if running from within a py.test run
--------------------------------------------------------------

Usually it is a bad idea to make application code
behave differently if called from a test.  But if you
absolutely must find out if your application code is
running from a test you can do something like this::

    # content of conftest.py in your testing directory

    def pytest_configure(config):
        import sys   
        sys._called_from_test = True

    def pytest_unconfigure(config):
        del sys._called_from_test

and then check for the ``sys._called_from_test`` flag::

    if hasattr(sys, '_called_from_test'):
        # called from within a test run
    else:
        # called "normally"
    
accordingly in your application.  It's also a good idea
to rather use your own application module rather than ``sys``
for handling flag.