diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 3df69ba..f3dd1b3 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -2545,10 +2545,8 @@ def getdict(self):
         m2instance.b = 2
         m2instance.a = 1
         self.assertEqual(m2instance.__dict__, "Not a dict!")
-        try:
+        with self.assertRaises(TypeError):
             dir(m2instance)
-        except TypeError:
-            pass
 
         # Two essentially featureless objects, (Ellipsis just inherits stuff
         # from object.
@@ -4062,7 +4060,7 @@ class D(C):
         except TypeError:
             pass
         else:
-            assert 0, "best_base calculation found wanting"
+            self.fail("best_base calculation found wanting")
 
     def test_unsubclassable_types(self):
         with self.assertRaises(TypeError):
@@ -4448,6 +4446,8 @@ def __getattr__(self, attr):
             print("Oops!")
         except RuntimeError:
             pass
+        else:
+            self.fail("Didn't raise RuntimeError")
         finally:
             sys.stdout = test_stdout