[compat] Add test for compat_casefold()

test/test_compat.py

@@ -118,9 +118,21 @@ class TestCompat(unittest.TestCase):
 <smil xmlns="http://www.w3.org/2001/SMIL20/Language"></smil>'''
         compat_etree_fromstring(xml)
 
-    def test_struct_unpack(self):
+    def test_compat_struct_unpack(self):
         self.assertEqual(compat_struct_unpack('!B', b'\x00'), (0,))
 
+    def test_compat_casefold(self):
+        if hasattr(compat_str, 'casefold'):
+            # don't bother to test str.casefold() (again)
+            return
+        # thanks https://bugs.python.org/file24232/casefolding.patch
+        self.assertEqual(compat_casefold('hello'), 'hello')
+        self.assertEqual(compat_casefold('hELlo'), 'hello')
+        self.assertEqual(compat_casefold('ß'), 'ss')
+        self.assertEqual(compat_casefold('fi'), 'fi')
+        self.assertEqual(compat_casefold('\u03a3'), '\u03c3')
+        self.assertEqual(compat_casefold('A\u0345\u03a3'), 'a\u03b9\u03c3')
+
 
 if __name__ == '__main__':
     unittest.main()