fixes issue 156: monkeypatch class level descriptors

CHANGELOG

@@ -56,7 +56,8 @@ Changes between 2.2.4 and 2.3.0.dev
 - fix issue 188: ensure sys.exc_info is clear on python2
                  before calling into a test
 
-- fix issue 191: addd unittest TestCase runTest method support
+- fix issue 191: add unittest TestCase runTest method support
+- fix issue 156: monkeypatch correctly handles class level descriptors
 
 - reporting refinements:
 

_pytest/monkeypatch.py

@@ -1,6 +1,6 @@
 """ monkeypatching and mocking functionality.  """
 
-import os, sys
+import os, sys, inspect
 
 def pytest_funcarg__monkeypatch(request):
     """The returned ``monkeypatch`` funcarg provides these
@@ -39,6 +39,10 @@ class monkeypatch:
         oldval = getattr(obj, name, notset)
         if raising and oldval is notset:
             raise AttributeError("%r has no attribute %r" %(obj, name))
+
+        # avoid class descriptors like staticmethod/classmethod
+        if inspect.isclass(obj):
+            oldval = obj.__dict__.get(name, notset)
         self._setattr.insert(0, (obj, name, oldval))
         setattr(obj, name, value)
 

testing/test_monkeypatch.py

@@ -206,3 +206,38 @@ def test_issue185_time_breaks(testdir):
     result.stdout.fnmatch_lines("""
         *1 passed*
     """)
+
+
+
+class SampleNew(object):
+    @staticmethod
+    def hello():
+        return True
+
+
+class SampleNewInherit(SampleNew):
+    pass
+
+
+class SampleOld:
+    #oldstyle on python2
+    @staticmethod
+    def hello():
+        return True
+
+class SampleOldInherit(SampleOld):
+    pass
+
+
+@pytest.mark.parametrize('Sample', [
+    SampleNew, SampleNewInherit,
+    SampleOld, SampleOldInherit,
+], ids=['new', 'new-inherit', 'old', 'old-inherit'])
+def test_issue156_undo_staticmethod(Sample):
+    monkeypatch = MonkeyPatch()
+
+    monkeypatch.setattr(Sample, 'hello', None)
+    assert Sample.hello is None
+
+    monkeypatch.undo()
+    assert Sample.hello()