Run add_missing_tags when testing and adding feed

tests/test_feeds.py

@@ -6,6 +6,7 @@ import pytest
 from reader import Feed, Reader, make_reader  # type: ignore
 
 from discord_rss_bot.feeds import send_to_discord
+from discord_rss_bot.missing_tags import add_missing_tags
 
 
 def test_send_to_discord() -> None:
@@ -22,6 +23,8 @@ def test_send_to_discord() -> None:
         # Add a feed to the reader.
         reader.add_feed("https://www.reddit.com/r/Python/.rss")
 
+        add_missing_tags(reader)
+
         # Update the feed to get the entries.
         reader.update_feeds()