setupstate.addfinalizer(): fix docstring and remove related unit test not covering functional reality

_pytest/runner.py

@@ -316,11 +316,10 @@ class SetupState(object):
         """ attach a finalizer to the given colitem.
         if colitem is None, this will add a finalizer that
         is called at the end of teardown_all().
-        if colitem is a tuple, it will be used as a key
-        and needs an explicit call to _callfinalizers(key) later on.
         """
-        assert hasattr(finalizer, '__call__')
-        #assert colitem in self.stack
+        assert colitem and not isinstance(colitem, tuple)
+        assert callable(finalizer)
+        #assert colitem in self.stack  # some unit tests don't setup stack :/
         self._finalizers.setdefault(colitem, []).append(finalizer)
 
     def _pop_and_teardown(self):

testing/test_runner.py

@@ -14,20 +14,6 @@ class TestSetupState:
         ss._pop_and_teardown()
         assert not l
 
-    def test_setup_scope_None(self, testdir):
-        item = testdir.getitem("def test_func(): pass")
-        ss = runner.SetupState()
-        l = [1]
-        ss.prepare(item)
-        ss.addfinalizer(l.pop, colitem=None)
-        assert l
-        ss._pop_and_teardown()
-        assert l
-        ss._pop_and_teardown()
-        assert l
-        ss.teardown_all()
-        assert not l
-
     def test_teardown_exact_stack_empty(self, testdir):
         item = testdir.getitem("def test_func(): pass")
         ss = runner.SetupState()