Various test fixes

vibe_bot/tests/test_main.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from datetime import UTC
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
@@ -44,8 +45,8 @@ def mock_ctx_with_member() -> MagicMock:
     ctx.author.activities = [mock_activity]
     from datetime import datetime
 
-    ctx.author.joined_at = datetime(2024, 1, 15)
-    ctx.author.created_at = datetime(2023, 6, 1)
+    ctx.author.joined_at = datetime(2024, 1, 15, tzinfo=UTC)
+    ctx.author.created_at = datetime(2023, 6, 1, tzinfo=UTC)
     ctx.channel.id = "channel-1"
     ctx.guild.id = "guild-1"
     ctx.message.id = "msg-1"
@@ -481,7 +482,6 @@ def test_speak_plain_with_mock_tts(
     asyncio.run(main_module._speak_plain(mock_ctx, "hello world", mock_tts_engine))
 
     from vibe_bot.config import TTS_SPEED, TTS_VOICE
-
     from vibe_bot.tts import DEFAULT_LANG
 
     mock_tts_engine.generate_audio.assert_called_once_with(