tests: added testcases for Message.from_file() and Message.to_file()

tests/test_message.py

@@ -230,6 +230,20 @@ This is an answer.
         message = Message.from_file(self.file_path, tags_or={Tag('tag3')})
         self.assertIsNone(message)
 
+    def test_from_file_txt_no_tags_dont_match(self) -> None:
+        message = Message.from_file(self.file_path_no_tags, tags_or={Tag('tag1')})
+        self.assertIsNone(message)
+
+    def test_from_file_txt_no_tags_match_tags_not(self) -> None:
+        message = Message.from_file(self.file_path_no_tags, tags_not={Tag('tag1')})
+        self.assertIsNotNone(message)
+        self.assertIsInstance(message, Message)
+        if message:
+            self.assertEqual(message.question, 'This is a question.')
+            self.assertEqual(message.answer, 'This is an answer.')
+            self.assertSetEqual(cast(set[Tag], message.tags), set())
+            self.assertEqual(message.file_path, self.file_path_no_tags)
+
     def test_from_file_not_exists(self) -> None:
         file_not_exists = pathlib.Path("example.txt")
         with self.assertRaises(MessageError) as cm: