Implement in terms of base addTest.

1 files changed, 3 insertions, 2 deletions

diff --git a/lib/testresources/__init__.py b/lib/testresources/__init__.py
index b4f965b..8e04cbe 100644
--- a/lib/testresources/__init__.py
+++ b/lib/testresources/__init__.py
@@ -57,14 +57,15 @@ class OptimisingTestSuite(unittest.TestSuite):
         try:
             tests = iter(test_case_or_suite)
         except TypeError:
-            self._tests.append(test_case_or_suite)
+            unittest.TestSuite.addTest(self, test_case_or_suite)
             return
         if unittest.TestSuite == test_case_or_suite.__class__:
             for test in tests:
                 self.adsorbSuite(test)
         else:
             for test in tests:
-                self._tests.append(test_case_or_suite.__class__([test]))
+                unittest.TestSuite.addTest(
+                    self, test_case_or_suite.__class__([test]))
 
     def cost_of_switching(self, old_resource_set, new_resource_set):
         """Cost of switching from 'old_resource_set' to 'new_resource_set'.