Remove device from known_devices upon import in ping device tracker (#105009)

Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

tests/components/device_tracker/test_legacy.py

@@ -0,0 +1,44 @@
+"""Tests for the legacy device tracker component."""
+from unittest.mock import mock_open, patch
+
+from homeassistant.components.device_tracker import legacy
+from homeassistant.core import HomeAssistant
+from homeassistant.util.yaml import dump
+
+from tests.common import patch_yaml_files
+
+
+def test_remove_device_from_config(hass: HomeAssistant):
+    """Test the removal of a device from a config."""
+    yaml_devices = {
+        "test": {
+            "hide_if_away": True,
+            "mac": "00:11:22:33:44:55",
+            "name": "Test name",
+            "picture": "/local/test.png",
+            "track": True,
+        },
+        "test2": {
+            "hide_if_away": True,
+            "mac": "00:ab:cd:33:44:55",
+            "name": "Test2",
+            "picture": "/local/test2.png",
+            "track": True,
+        },
+    }
+    mopen = mock_open()
+
+    files = {legacy.YAML_DEVICES: dump(yaml_devices)}
+    with patch_yaml_files(files, True), patch(
+        "homeassistant.components.device_tracker.legacy.open", mopen
+    ):
+        legacy.remove_device_from_config(hass, "test")
+
+    mopen().write.assert_called_once_with(
+        "test2:\n"
+        "  hide_if_away: true\n"
+        "  mac: 00:ab:cd:33:44:55\n"
+        "  name: Test2\n"
+        "  picture: /local/test2.png\n"
+        "  track: true\n"
+    )