Fix pico tts errors (#41619)

Enabled the use of mutagen in unit tests.
Added a test for tagging a minimal .wav file.

tests/components/tts/test_init.py

@@ -73,7 +73,7 @@ def empty_cache_dir(tmp_path, mock_init_cache_dir, mock_get_cache_files, request
     assert False
 
 
-@pytest.fixture(autouse=True)
+@pytest.fixture()
 def mutagen_mock():
     """Mock writing tags."""
     with patch(
@@ -480,7 +480,7 @@ async def test_setup_component_and_test_service_with_receive_voice(
         "42f18378fd4393d18c8dd11d03fa9563c1e54491_en_-_demo.mp3",
         demo_data,
         demo_provider,
-        "AI person is in front of your door.",
+        "There is someone at the door.",
         "en",
         None,
     )
@@ -716,3 +716,24 @@ async def test_setup_component_and_web_get_url_bad_config(hass, hass_client):
 
     req = await client.post(url, json=data)
     assert req.status == 400
+
+
+async def test_tags_with_wave(hass, demo_provider):
+    """Set up the demo platform and call service and receive voice."""
+
+    # below data represents an empty wav file
+    demo_data = bytes.fromhex(
+        "52 49 46 46 24 00 00 00 57 41 56 45 66 6d 74 20 10 00 00 00 01 00 02 00"
+        + "22 56 00 00 88 58 01 00 04 00 10 00 64 61 74 61 00 00 00 00"
+    )
+
+    tagged_data = tts.SpeechManager.write_tags(
+        "42f18378fd4393d18c8dd11d03fa9563c1e54491_en_-_demo.wav",
+        demo_data,
+        demo_provider,
+        "AI person is in front of your door.",
+        "en",
+        None,
+    )
+
+    assert tagged_data != demo_data