make the test more fine granular

theano/tensor/nnet/tests/test_conv.py

@@ -175,7 +175,17 @@ class TestConv2D(unittest.TestCase):
         """
         try:
             self.validate((3,2,8,8), (4,2,5,5), 'valid', input = T.dmatrix())
+            # should never reach here
+            self.fail()
+        except: 
+            pass
+        try:
             self.validate((3,2,8,8), (4,2,5,5), 'valid', filters = T.dvector())
+            # should never reach here
+            self.fail()
+        except: 
+            pass
+        try:
             self.validate((3,2,8,8), (4,2,5,5), 'valid', input = T.dtensor3())
             # should never reach here
             self.fail()