#!python

from mock import Mock

class Sample(object):
    @staticmethod
    def hello():
        return True

def test_1(monkeypatch):
    monkeypatch.setattr(Sample, 'hello', Mock(return_value=False))
    assert not Sample.hello()

def test_2():
    assert Sample.hello()





#!python

$ py.test -v pytest_bug.py 
================================== test session starts ==================================
platform linux2 -- Python 2.7.3 -- pytest-2.2.4 -- /home/eduardo/work/py27/bin/python
collected 2 items 

pytest_bug.py:8: test_1 PASSED
pytest_bug.py:12: test_2 FAILED

======================================= FAILURES ========================================
________________________________________ test_2 _________________________________________

    def test_2():
>       assert Sample.hello()
E       TypeError: unbound method hello() must be called with Sample instance as first argument (got nothing instead)

pytest_bug.py:13: TypeError
========================== 1 failed, 1 passed in 0.01 seconds ===========================




#!python

 py.test -v pytest_bug.py -k test_2
================================== test session starts ==================================
platform linux2 -- Python 2.7.3 -- pytest-2.2.4 -- /home/eduardo/work/py27/bin/python
collected 2 items 

pytest_bug.py:12: test_2 PASSED

=========================== 1 tests deselected by '-ktest_2' ============================
======================== 1 passed, 1 deselected in 0.01 seconds =========================