Improve test coverage and add comment for loading in executor for remote calendar (#140807)

Improve calendar loading by executing in a separate thread and add test for CalendarParseError

homeassistant/components/remote_calendar/coordinator.py

@@ -56,6 +56,9 @@ class RemoteCalendarDataUpdateCoordinator(DataUpdateCoordinator[Calendar]):
                 translation_placeholders={"err": str(err)},
             ) from err
         try:
+            # calendar_from_ics will dynamically load packages
+            # the first time it is called, so we need to do it
+            # in a separate thread to avoid blocking the event loop
             return await self.hass.async_add_executor_job(
                 IcsCalendarStream.calendar_from_ics, res.text
             )

tests/components/remote_calendar/test_init.py

@@ -71,3 +71,16 @@ async def test_update_failed(
     respx.get(CALENDER_URL).mock(side_effect=side_effect)
     await setup_integration(hass, config_entry)
     assert config_entry.state is ConfigEntryState.SETUP_RETRY
+
+
+@respx.mock
+async def test_calendar_parse_error(
+    hass: HomeAssistant,
+    config_entry: MockConfigEntry,
+) -> None:
+    """Test CalendarParseError using respx."""
+    respx.get(CALENDER_URL).mock(
+        return_value=Response(status_code=200, text="not a calendar")
+    )
+    await setup_integration(hass, config_entry)
+    assert config_entry.state is ConfigEntryState.SETUP_RETRY