diff --git a/testtools/testcase.py b/testtools/testcase.py
index 004fdb5..b8e9010 100644
--- a/testtools/testcase.py
+++ b/testtools/testcase.py
@@ -693,7 +693,17 @@ class TestCase(unittest.TestCase):
 
     def _get_test_method(self):
         method_name = getattr(self, '_testMethodName')
-        return getattr(self, method_name)
+        try:
+            m = getattr(self, method_name)
+        except AttributeError:
+            if method_name != "runTest":
+                # We allow instantiation with no explicit method name
+                # but not an *incorrect* or missing method name.
+                raise ValueError(
+                        "no such test method in %s: %s" % (self.__class__, method_name)
+                )
+        else:
+          return m
 
     def _run_test_method(self, result):
         """Run the test method for this test.