Replace with more useful test case

Author: hugovk

Lib/test/test_mimetypes.py

@@ -307,8 +307,13 @@ def test_keywords_args_api(self):
             type='image/jpg', strict=False), '.jpg')
 
     def test_added_types_are_used(self):
+        mimetypes.add_type('testing/default-type', '')
+        mime_type, _ = mimetypes.guess_type('')
+        self.assertEqual(mime_type, 'testing/default-type')
+
         mime_type, _ = mimetypes.guess_type('test.myext')
         self.assertEqual(mime_type, None)
+
         mimetypes.add_type('testing/type', '.myext')
         mime_type, _ = mimetypes.guess_type('test.myext')
         self.assertEqual(mime_type, 'testing/type')
@@ -319,11 +324,6 @@ def test_add_type_with_undotted_extension_raises_exception(self):
         ):
             mimetypes.add_type('testing/type', 'undotted')
 
-    def test_add_type_with_empty_extension_emits_no_warning(self):
-        with warnings.catch_warnings(record=True) as wlog:
-            mimetypes.add_type('testing/type', '')
-        self.assertEqual(len(wlog), 0)
-
 
 @unittest.skipUnless(sys.platform.startswith("win"), "Windows only")
 class Win32MimeTypesTestCase(unittest.TestCase):