Test guess_file_type with types with multiple extensions

Author: hugovk

Lib/test/test_mimetypes.py

@@ -287,6 +287,27 @@ def check_extensions():
         mimetypes.init()
         check_extensions()
 
+    def test_guess_file_type(self):
+        def check_file_type():
+            for mime_type, ext in (
+                ("application/yaml", ".yaml"),
+                ("application/yaml", ".yml"),
+                ("audio/mpeg", ".mp2"),
+                ("audio/mpeg", ".mp3"),
+                ("video/mpeg", ".m1v"),
+                ("video/mpeg", ".mpa"),
+                ("video/mpeg", ".mpe"),
+                ("video/mpeg", ".mpeg"),
+                ("video/mpeg", ".mpg"),
+            ):
+                with self.subTest(mime_type=mime_type, ext=ext):
+                    result, _ = mimetypes.guess_file_type(f"filename{ext}")
+                    self.assertEqual(result, mime_type)
+
+        check_file_type()
+        mimetypes.init()
+        check_file_type()
+
     def test_init_stability(self):
         mimetypes.init()