[utils][tests][dir2] Improve test_misbehaving_object_without_trait_names

IPython/utils/tests/test_dir2.py

@@ -1,5 +1,7 b''
 from IPython.utils.dir2 import dir2
 
+import pytest
+
 
 class Base(object):
     x = 1
@@ -35,24 +37,31 b' def test_SubClass_with_trait_names_attr():'
         trait_names = 44
 
     res = dir2(SubClass())
-    assert('trait_names' in res)
+    assert "trait_names" in res
 
 
 def test_misbehaving_object_without_trait_names():
     # dir2 shouldn't raise even when objects are dumb and raise
     # something other than AttribteErrors on bad getattr.
 
-    class MisbehavingGetattr(object):
-        def __getattr__(self):
+    class MisbehavingGetattr:
+        def __getattr__(self, attr):
             raise KeyError("I should be caught")
 
         def some_method(self):
-            pass
+            return True
 
     class SillierWithDir(MisbehavingGetattr):
         def __dir__(self):
             return ['some_method']
 
     for bad_klass in (MisbehavingGetattr, SillierWithDir):
-        res = dir2(bad_klass())
-        assert('some_method' in res)
+        obj = bad_klass()
+
+        assert obj.some_method()
+
+        with pytest.raises(KeyError):
+            obj.other_method()
+
+        res = dir2(obj)
+        assert "some_method" in res