check signal types in dg.plug

While here, develop test from previous commit, and fix another test in
the same file.

fix #36

Author: nim65s

src/dynamic_graph/dynamic-graph-py.cc

@@ -40,8 +40,10 @@ PyObject* plug(PyObject* /*self*/, PyObject* args) {
 
   pObjIn = PyCapsule_GetPointer(objIn, "dynamic_graph.Signal");
   SignalBase<int>* signalIn = (SignalBase<int>*)pObjIn;
+  if (signalIn == NULL) return NULL;
   pObjOut = PyCapsule_GetPointer(objOut, "dynamic_graph.Signal");
   SignalBase<int>* signalOut = (SignalBase<int>*)pObjOut;
+  if (signalOut == NULL) return NULL;
   std::ostringstream os;
 
   try {

unitTesting/test_bindings.py

@@ -6,18 +6,19 @@
 
 class BindingsTests(unittest.TestCase):
     def test_bindings(self):
-        with self.assertRaises(Exception) as error:
+        with self.assertRaises(Exception) as cm:
             dg.error_out()
-            self.assertEqual(str(error), "something bad happend")
+        self.assertEqual(str(cm.exception), "something bad happened")
 
     def test_type_check(self):
         first = CustomEntity('first_entity')
         second = CustomEntity('second_entity')
         # Check that we can connect first.out to second.in
         dg.plug(first.signal('out_double'), second.signal('in_double'))
         # Check that we can't connect first.out to second
-        with self.assertRaises(Exception):
+        with self.assertRaises(ValueError) as cm:
             dg.plug(first.signal('out_double'), second)
+        self.assertEqual(str(cm.exception), "PyCapsule_GetPointer called with incorrect name")
 
 
 if __name__ == '__main__':