Add some basic tests for PyrexTypes.widest_numeric_type().

Cython/Compiler/Tests/TestTypes.py

+from __future__ import absolute_import
+
+import unittest
+
+import Cython.Compiler.PyrexTypes as PT
+
+
+class TestMethodDispatcherTransform(unittest.TestCase):
+
+    def test_widest_numeric_type(self):
+        def assert_widest(type1, type2, widest):
+            self.assertEqual(widest, PT.widest_numeric_type(type1, type2))
+
+        assert_widest(PT.c_int_type, PT.c_long_type, PT.c_long_type)
+        assert_widest(PT.c_double_type, PT.c_long_type, PT.c_double_type)
+        assert_widest(PT.c_longdouble_type, PT.c_long_type, PT.c_longdouble_type)
+
+        cenum = PT.CEnumType("E", "cenum", typedef_flag=False)
+        assert_widest(PT.c_int_type, cenum, PT.c_int_type)