diff --git a/tests/components/demo/test_init.py b/tests/components/demo/test_init.py
index b00028e34d9..fa0aff8223b 100644
--- a/tests/components/demo/test_init.py
+++ b/tests/components/demo/test_init.py
@@ -1,12 +1,10 @@
 """The tests for the Demo component."""
-from contextlib import suppress
 import json
-import os
+from unittest.mock import patch
 
 import pytest
 
 from homeassistant.components.demo import DOMAIN
-from homeassistant.components.device_tracker.legacy import YAML_DEVICES
 from homeassistant.components.recorder import get_instance
 from homeassistant.components.recorder.statistics import list_statistic_ids
 from homeassistant.helpers.json import JSONEncoder
@@ -22,11 +20,10 @@ def mock_history(hass):
 
 
 @pytest.fixture(autouse=True)
-def demo_cleanup(hass):
-    """Clean up device tracker demo file."""
-    yield
-    with suppress(FileNotFoundError):
-        os.remove(hass.config.path(YAML_DEVICES))
+def mock_device_tracker_update_config(hass):
+    """Prevent device tracker from creating known devices file."""
+    with patch("homeassistant.components.device_tracker.legacy.update_config"):
+        yield
 
 
 async def test_setting_up_demo(hass):
diff --git a/tests/components/device_tracker/test_init.py b/tests/components/device_tracker/test_init.py
index 0953fc67b0a..d8914032f36 100644
--- a/tests/components/device_tracker/test_init.py
+++ b/tests/components/device_tracker/test_init.py
@@ -28,6 +28,8 @@ from homeassistant.helpers.json import JSONEncoder
 from homeassistant.setup import async_setup_component
 import homeassistant.util.dt as dt_util
 
+from . import common
+
 from tests.common import (
     assert_setup_component,
     async_fire_time_changed,
@@ -35,7 +37,6 @@ from tests.common import (
     mock_restore_cache,
     patch_yaml_files,
 )
-from tests.components.device_tracker import common
 
 TEST_PLATFORM = {device_tracker.DOMAIN: {CONF_PLATFORM: "test"}}
 
@@ -165,6 +166,7 @@ async def test_setup_without_yaml_file(hass, enable_custom_integrations):
     """Test with no YAML file."""
     with assert_setup_component(1, device_tracker.DOMAIN):
         assert await async_setup_component(hass, device_tracker.DOMAIN, TEST_PLATFORM)
+        await hass.async_block_till_done()
 
 
 async def test_gravatar(hass):
@@ -210,10 +212,11 @@ async def test_gravatar_and_picture(hass):
 @patch("homeassistant.components.demo.device_tracker.setup_scanner", autospec=True)
 async def test_discover_platform(mock_demo_setup_scanner, mock_see, hass):
     """Test discovery of device_tracker demo platform."""
-    await discovery.async_load_platform(
-        hass, device_tracker.DOMAIN, "demo", {"test_key": "test_val"}, {"bla": {}}
-    )
-    await hass.async_block_till_done()
+    with patch("homeassistant.components.device_tracker.legacy.update_config"):
+        await discovery.async_load_platform(
+            hass, device_tracker.DOMAIN, "demo", {"test_key": "test_val"}, {"bla": {}}
+        )
+        await hass.async_block_till_done()
     assert device_tracker.DOMAIN in hass.config.components
     assert mock_demo_setup_scanner.called
     assert mock_demo_setup_scanner.call_args[0] == (