Add diagnostics platform to airgradient (#126886)

tests/components/airgradient/test_diagnostics.py

@@ -0,0 +1,29 @@
+"""Tests for the diagnostics data provided by the AirGradient integration."""
+
+from unittest.mock import AsyncMock
+
+from syrupy import SnapshotAssertion
+
+from homeassistant.core import HomeAssistant
+
+from . import setup_integration
+
+from tests.common import MockConfigEntry
+from tests.components.diagnostics import get_diagnostics_for_config_entry
+from tests.typing import ClientSessionGenerator
+
+
+async def test_diagnostics_polling_instance(
+    hass: HomeAssistant,
+    hass_client: ClientSessionGenerator,
+    mock_airgradient_client: AsyncMock,
+    mock_config_entry: MockConfigEntry,
+    snapshot: SnapshotAssertion,
+) -> None:
+    """Test diagnostics."""
+    await setup_integration(hass, mock_config_entry)
+
+    assert (
+        await get_diagnostics_for_config_entry(hass, hass_client, mock_config_entry)
+        == snapshot
+    )