diff --git a/homeassistant/components/nest/diagnostics.py b/homeassistant/components/nest/diagnostics.py
index 0b6cfff6bae..859aa834581 100644
--- a/homeassistant/components/nest/diagnostics.py
+++ b/homeassistant/components/nest/diagnostics.py
@@ -12,7 +12,7 @@ from google_nest_sdm.exceptions import ApiException
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.core import HomeAssistant
 
-from .const import DATA_SUBSCRIBER, DOMAIN
+from .const import DATA_SDM, DATA_SUBSCRIBER, DOMAIN
 
 REDACT_DEVICE_TRAITS = {InfoTrait.NAME}
 
@@ -21,6 +21,9 @@ async def async_get_config_entry_diagnostics(
     hass: HomeAssistant, config_entry: ConfigEntry
 ) -> dict:
     """Return diagnostics for a config entry."""
+    if DATA_SDM not in config_entry.data:
+        return {}
+
     if DATA_SUBSCRIBER not in hass.data[DOMAIN]:
         return {"error": "No subscriber configured"}
 
diff --git a/tests/components/nest/common.py b/tests/components/nest/common.py
index ca761e8987f..e80ca84d58f 100644
--- a/tests/components/nest/common.py
+++ b/tests/components/nest/common.py
@@ -102,6 +102,24 @@ TEST_CONFIG_HYBRID = NestTestConfig(
     },
 )
 
+TEST_CONFIG_LEGACY = NestTestConfig(
+    config={
+        "nest": {
+            "client_id": "some-client-id",
+            "client_secret": "some-client-secret",
+        },
+    },
+    config_entry_data={
+        "auth_implementation": "local",
+        "tokens": {
+            "expires_at": time.time() + 86400,
+            "access_token": {
+                "token": "some-token",
+            },
+        },
+    },
+)
+
 
 class FakeSubscriber(GoogleNestSubscriber):
     """Fake subscriber that supplies a FakeDeviceManager."""
diff --git a/tests/components/nest/test_config_flow_legacy.py b/tests/components/nest/test_config_flow_legacy.py
index d21920b9e6f..843c9b582ae 100644
--- a/tests/components/nest/test_config_flow_legacy.py
+++ b/tests/components/nest/test_config_flow_legacy.py
@@ -6,9 +6,11 @@ from homeassistant import config_entries, data_entry_flow
 from homeassistant.components.nest import DOMAIN, config_flow
 from homeassistant.setup import async_setup_component
 
+from .common import TEST_CONFIG_LEGACY
+
 from tests.common import MockConfigEntry
 
-CONFIG = {DOMAIN: {"client_id": "bla", "client_secret": "bla"}}
+CONFIG = TEST_CONFIG_LEGACY.config
 
 
 async def test_abort_if_no_implementation_registered(hass):
@@ -59,7 +61,7 @@ async def test_full_flow_implementation(hass):
     assert (
         result["description_placeholders"]
         .get("url")
-        .startswith("https://home.nest.com/login/oauth2?client_id=bla")
+        .startswith("https://home.nest.com/login/oauth2?client_id=some-client-id")
     )
 
     def mock_login(auth):
diff --git a/tests/components/nest/test_diagnostics.py b/tests/components/nest/test_diagnostics.py
index b603019da81..cf6c9c5b20f 100644
--- a/tests/components/nest/test_diagnostics.py
+++ b/tests/components/nest/test_diagnostics.py
@@ -2,54 +2,45 @@
 
 from unittest.mock import patch
 
-from google_nest_sdm.device import Device
 from google_nest_sdm.exceptions import SubscriberException
+import pytest
 
-from homeassistant.components.nest import DOMAIN
 from homeassistant.config_entries import ConfigEntryState
-from homeassistant.setup import async_setup_component
 
-from .common import CONFIG, async_setup_sdm_platform, create_config_entry
+from .common import TEST_CONFIG_LEGACY
 
 from tests.components.diagnostics import get_diagnostics_for_config_entry
 
-THERMOSTAT_TYPE = "sdm.devices.types.THERMOSTAT"
 
-
-async def test_entry_diagnostics(hass, hass_client):
+async def test_entry_diagnostics(
+    hass, hass_client, create_device, setup_platform, config_entry
+):
     """Test config entry diagnostics."""
-    devices = {
-        "some-device-id": Device.MakeDevice(
-            {
-                "name": "enterprises/project-id/devices/device-id",
-                "type": "sdm.devices.types.THERMOSTAT",
-                "assignee": "enterprises/project-id/structures/structure-id/rooms/room-id",
-                "traits": {
-                    "sdm.devices.traits.Info": {
-                        "customName": "My Sensor",
-                    },
-                    "sdm.devices.traits.Temperature": {
-                        "ambientTemperatureCelsius": 25.1,
-                    },
-                    "sdm.devices.traits.Humidity": {
-                        "ambientHumidityPercent": 35.0,
-                    },
+    create_device.create(
+        raw_data={
+            "name": "enterprises/project-id/devices/device-id",
+            "type": "sdm.devices.types.THERMOSTAT",
+            "assignee": "enterprises/project-id/structures/structure-id/rooms/room-id",
+            "traits": {
+                "sdm.devices.traits.Info": {
+                    "customName": "My Sensor",
+                },
+                "sdm.devices.traits.Temperature": {
+                    "ambientTemperatureCelsius": 25.1,
+                },
+                "sdm.devices.traits.Humidity": {
+                    "ambientHumidityPercent": 35.0,
                 },
-                "parentRelations": [
-                    {
-                        "parent": "enterprises/project-id/structures/structure-id/rooms/room-id",
-                        "displayName": "Lobby",
-                    }
-                ],
             },
-            auth=None,
-        )
-    }
-    assert await async_setup_sdm_platform(hass, platform=None, devices=devices)
-
-    entries = hass.config_entries.async_entries(DOMAIN)
-    assert len(entries) == 1
-    config_entry = entries[0]
+            "parentRelations": [
+                {
+                    "parent": "enterprises/project-id/structures/structure-id/rooms/room-id",
+                    "displayName": "Lobby",
+                }
+            ],
+        }
+    )
+    await setup_platform()
     assert config_entry.state is ConfigEntryState.LOADED
 
     # Test that only non identifiable device information is returned
@@ -76,20 +67,32 @@ async def test_entry_diagnostics(hass, hass_client):
     }
 
 
-async def test_setup_susbcriber_failure(hass, hass_client):
+async def test_setup_susbcriber_failure(
+    hass, hass_client, config_entry, setup_base_platform
+):
     """Test configuration error."""
-    config_entry = create_config_entry()
-    config_entry.add_to_hass(hass)
     with patch(
         "homeassistant.helpers.config_entry_oauth2_flow.async_get_config_entry_implementation"
     ), patch(
         "homeassistant.components.nest.api.GoogleNestSubscriber.start_async",
         side_effect=SubscriberException(),
     ):
-        assert await async_setup_component(hass, DOMAIN, CONFIG)
+        await setup_base_platform()
 
     assert config_entry.state is ConfigEntryState.SETUP_RETRY
 
     assert await get_diagnostics_for_config_entry(hass, hass_client, config_entry) == {
         "error": "No subscriber configured"
     }
+
+
+@pytest.mark.parametrize("nest_test_config", [TEST_CONFIG_LEGACY])
+async def test_legacy_config_entry_diagnostics(
+    hass, hass_client, config_entry, setup_base_platform
+):
+    """Test config entry diagnostics for legacy integration doesn't fail."""
+
+    with patch("homeassistant.components.nest.legacy.Nest"):
+        await setup_base_platform()
+
+    assert await get_diagnostics_for_config_entry(hass, hass_client, config_entry) == {}
diff --git a/tests/components/nest/test_init_legacy.py b/tests/components/nest/test_init_legacy.py
index 3a78877a235..cbf1bfe2d48 100644
--- a/tests/components/nest/test_init_legacy.py
+++ b/tests/components/nest/test_init_legacy.py
@@ -1,30 +1,18 @@
 """Test basic initialization for the Legacy Nest API using mocks for the Nest python library."""
 
-import time
 from unittest.mock import MagicMock, PropertyMock, patch
 
-from homeassistant.setup import async_setup_component
+import pytest
 
-from tests.common import MockConfigEntry
+from .common import TEST_CONFIG_LEGACY
 
 DOMAIN = "nest"
 
-CONFIG = {
-    "nest": {
-        "client_id": "some-client-id",
-        "client_secret": "some-client-secret",
-    },
-}
 
-CONFIG_ENTRY_DATA = {
-    "auth_implementation": "local",
-    "tokens": {
-        "expires_at": time.time() + 86400,
-        "access_token": {
-            "token": "some-token",
-        },
-    },
-}
+@pytest.fixture
+def nest_test_config():
+    """Fixture to specify the overall test fixture configuration."""
+    return TEST_CONFIG_LEGACY
 
 
 def make_thermostat():
@@ -45,7 +33,7 @@ def make_thermostat():
     return device
 
 
-async def test_thermostat(hass):
+async def test_thermostat(hass, setup_base_platform):
     """Test simple initialization for thermostat entities."""
 
     thermostat = make_thermostat()
@@ -58,8 +46,6 @@ async def test_thermostat(hass):
     nest = MagicMock()
     type(nest).structures = PropertyMock(return_value=[structure])
 
-    config_entry = MockConfigEntry(domain=DOMAIN, data=CONFIG_ENTRY_DATA)
-    config_entry.add_to_hass(hass)
     with patch("homeassistant.components.nest.legacy.Nest", return_value=nest), patch(
         "homeassistant.components.nest.legacy.sensor._VALID_SENSOR_TYPES",
         ["humidity", "temperature"],
@@ -67,8 +53,7 @@ async def test_thermostat(hass):
         "homeassistant.components.nest.legacy.binary_sensor._VALID_BINARY_SENSOR_TYPES",
         {"fan": None},
     ):
-        assert await async_setup_component(hass, DOMAIN, CONFIG)
-        await hass.async_block_till_done()
+        await setup_base_platform()
 
     climate = hass.states.get("climate.my_thermostat")
     assert climate is not None