diff --git a/tests/test_trees.py b/tests/test_trees.py
index 730b80b..82bf6c9 100644
--- a/tests/test_trees.py
+++ b/tests/test_trees.py
@@ -264,10 +264,7 @@ class TestTrees(TestCase):
             main = sum
             start = list
             def module__main(self, children):
-                prod = 1
-                for child in children:
-                    prod *= child
-                return prod
+                return sum(children)
 
         class T2(Transformer):
             A = int
@@ -277,25 +274,21 @@ class TestTrees(TestCase):
 
         class T3(Transformer):
             def main(self, children):
-                prod = 1
-                for child in children:
-                    prod *= child
-                return prod
+                return sum(children)
 
         class T4(Transformer):
-            def other_aspect(self, children):
-                pass
+            main = sum
+
 
         t1_res = T1().transform(tree)
         composed_res = merge_transformers(T2(), module=T3()).transform(tree)
         self.assertEqual(t1_res, composed_res)
+
+        composed_res2 = merge_transformers(T2(), module=T4()).transform(tree)
+        self.assertEqual(t1_res, composed_res2)
+
         with self.assertRaises(AttributeError):
             merge_transformers(T1(), module=T3())
 
-        try:
-            composed = merge_transformers(T1(), module=T4())
-        except AttributeError:
-            self.fail("Should be able to add classes that do not conflict")
-
 if __name__ == '__main__':
     unittest.main()