Minor test improvements

test_object.py was trying to call methods that were no longer
publicly available. This passed because it was checking for
errors (just not the ones being raised).
Improve test_channel.py and test_normMap.py to test for a
more explicit exception when using assertRaises.
I checked the usage in other tests and concluded it was best
to leave them as is because in some cases it wasn't clear which
C++ exception would be mapped to the Python exception that was
raised, and in others it was unclear if AST or C++ code would
catch the problem, thus which Python exception would be raised.

tests/test_channel.py

@@ -24,7 +24,7 @@ def test_ChannelFileStream(self):
         nobj = outchan.write(zoommap)
         self.assertEqual(nobj, 1)
 
-        with self.assertRaises(Exception):
+        with self.assertRaises(RuntimeError):
             obj = outchan.read()
 
         instream = astshim.FileStream(path1, False)

tests/test_normMap.py

@@ -34,7 +34,7 @@ def test_NormMapFrame(self):
 
     def testNormMapMap(self):
         """Check that NormMap(Mapping) is an error"""
-        with self.assertRaises(Exception):
+        with self.assertRaises(TypeError):
             astshim.NormMap(astshim.UnitMap(1))
 
     def test_NormMapSkyFrame(self):

tests/test_object.py

@@ -24,23 +24,6 @@ def test_attributes(self):
         self.assertEqual(obj.getIdent(), "")
         self.assertEqual(obj.getUseDefs(), True)
 
-    def test_unknown_attributes(self):
-        """Test accessing unknown attributes"""
-        obj = astshim.ZoomMap(2, 1.3)
-
-        self.assertFalse(obj.hasAttribute("NonExistentAttribute"))
-
-        with self.assertRaises(Exception):
-            obj.getC("NonExistentAttribute")
-        with self.assertRaises(Exception):
-            obj.getF("NonExistentAttribute")
-        with self.assertRaises(Exception):
-            obj.getD("NonExistentAttribute")
-        with self.assertRaises(Exception):
-            obj.getI("NonExistentAttribute")
-        with self.assertRaises(Exception):
-            obj.getL("NonExistentAttribute")
-
     def test_clear_and_test(self):
         """Test Object.clear and Object.test"""
         obj = astshim.ZoomMap(2, 1.3)