py.test main() invocation examples

I have this structure.

 /bin 
   __init__.py
   run_test.py (call pytest.main)
 /tests
   __init__.py
   test_xyz.py

If I call run_test.py using simply via pytest.main(), it won't invoke tests in "tests" module. I tried passing couple of parameters like module="tests" etc but they don't work. I have to altogether chuck auto discovery and use the suite parameter for it to pick up any tests.

What am I missing? I tried to walk through the code in the pytest module, but it is way too complex to understand. And the documentation is very bad.