[utils] Improve subtitles_filename (closes #22753)

1 files changed, 6 insertions, 0 deletions

diff --git a/test/test_utils.py b/test/test_utils.py
index 659c6ece5..3920542bb 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -74,6 +74,7 @@ from youtube_dl.utils import (
     str_to_int,
     strip_jsonp,
     strip_or_none,
+    subtitles_filename,
     timeconvert,
     unescapeHTML,
     unified_strdate,
@@ -261,6 +262,11 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(replace_extension('.abc', 'temp'), '.abc.temp')
         self.assertEqual(replace_extension('.abc.ext', 'temp'), '.abc.temp')
 
+    def test_subtitles_filename(self):
+        self.assertEqual(subtitles_filename('abc.ext', 'en', 'vtt'), 'abc.en.vtt')
+        self.assertEqual(subtitles_filename('abc.ext', 'en', 'vtt', 'ext'), 'abc.en.vtt')
+        self.assertEqual(subtitles_filename('abc.unexpected_ext', 'en', 'vtt', 'ext'), 'abc.unexpected_ext.en.vtt')
+
     def test_remove_start(self):
         self.assertEqual(remove_start(None, 'A - '), None)
         self.assertEqual(remove_start('A - B', 'A - '), 'B')