diff --git a/pyschlage/auth.py b/pyschlage/auth.py
index 1cb980d..e2bedba 100644
--- a/pyschlage/auth.py
+++ b/pyschlage/auth.py
@@ -76,6 +76,17 @@ def authenticate(self):
         """
         self.auth(requests.Request())
 
+    @property
+    def user_id(self) -> str:
+        """Returns the unique user id for the authenticated user."""
+        if self._user_id is None:
+            self._user_id = self._get_user_id()
+        return self._user_id
+
+    def _get_user_id(self) -> str:
+        resp = self.request("get", "users/@me")
+        return resp.json()["identityId"]
+
     @translate_errors
     def request(
         self, method: str, path: str, base_url: str = BASE_URL, **kwargs
diff --git a/tests/test_auth.py b/tests/test_auth.py
index 90addec..432563c 100644
--- a/tests/test_auth.py
+++ b/tests/test_auth.py
@@ -34,3 +34,60 @@ def test_request(mock_cognito, mock_srp_auth, mock_request):
         headers={"X-Api-Key": _auth.API_KEY},
         baz="bam",
     )
+
+
+@mock.patch("requests.request")
+@mock.patch("pycognito.utils.RequestsSrpAuth")
+@mock.patch("pycognito.Cognito")
+def test_user_id(mock_cognito, mock_srp_auth, mock_request):
+    auth = _auth.Auth("__username__", "__password__")
+    mock_request.return_value = mock.Mock(
+        json=mock.Mock(
+            return_value={
+                "consentRecords": [],
+                "created": "2022-12-24T20:00:00.000Z",
+                "email": "asdf@asdf.com",
+                "friendlyName": "username",
+                "identityId": "<user-id>",
+                "lastUpdated": "2022-12-24T20:00:00.000Z",
+            }
+        )
+    )
+    assert auth.user_id == "<user-id>"
+    mock_request.assert_called_once_with(
+        "get",
+        "https://api.allegion.yonomi.cloud/v1/users/@me",
+        timeout=60,
+        auth=mock_srp_auth.return_value,
+        headers={"X-Api-Key": _auth.API_KEY},
+    )
+
+
+@mock.patch("requests.request")
+@mock.patch("pycognito.utils.RequestsSrpAuth")
+@mock.patch("pycognito.Cognito")
+def test_user_id_is_cached(mock_cognito, mock_srp_auth, mock_request):
+    auth = _auth.Auth("__username__", "__password__")
+    mock_request.return_value = mock.Mock(
+        json=mock.Mock(
+            return_value={
+                "consentRecords": [],
+                "created": "2022-12-24T20:00:00.000Z",
+                "email": "asdf@asdf.com",
+                "friendlyName": "username",
+                "identityId": "<user-id>",
+                "lastUpdated": "2022-12-24T20:00:00.000Z",
+            }
+        )
+    )
+    assert auth.user_id == "<user-id>"
+    mock_request.assert_called_once_with(
+        "get",
+        "https://api.allegion.yonomi.cloud/v1/users/@me",
+        timeout=60,
+        auth=mock_srp_auth.return_value,
+        headers={"X-Api-Key": _auth.API_KEY},
+    )
+    mock_request.reset_mock()
+    assert auth.user_id == "<user-id>"
+    mock_request.assert_not_called()
diff --git a/tests/test_code.py b/tests/test_code.py
index 34ab276..f744d95 100644
--- a/tests/test_code.py
+++ b/tests/test_code.py
@@ -3,12 +3,13 @@
 from unittest import mock
 
 import pyschlage
+from pyschlage.auth import Auth
 from pyschlage.code import AccessCode, DaysOfWeek, RecurringSchedule, TemporarySchedule
 
 
 class TestAccessCode:
     def test_to_from_json(self, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         device_id = "__device_uuid__"
         access_code_id = "__access_code_uuid__"
         code = AccessCode(
@@ -27,7 +28,7 @@ def test_to_from_json(self, access_code_json):
         assert code.to_json() == want_json
 
     def test_to_from_json_recurring_schedule(self, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         device_id = "__device_uuid__"
         access_code_id = "__access_code_uuid__"
         sched = RecurringSchedule(days_of_week=DaysOfWeek(mon=False))
@@ -48,7 +49,7 @@ def test_to_from_json_recurring_schedule(self, access_code_json):
         assert code.to_json() == json
 
     def test_to_from_json_temporary_schedule(self, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         device_id = "__device_uuid__"
         access_code_id = "__access_code_uuid__"
         sched = TemporarySchedule(
@@ -73,7 +74,7 @@ def test_to_from_json_temporary_schedule(self, access_code_json):
         assert code.to_json() == json
 
     def test_refresh(self, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         code = AccessCode.from_json(auth, access_code_json, "__device_uuid__")
         new_json = deepcopy(access_code_json)
         new_json["accessCode"] = 1122
@@ -87,7 +88,7 @@ def test_refresh(self, access_code_json):
         assert code.code == "1122"
 
     def test_save(self, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         code = AccessCode.from_json(auth, access_code_json, "__device_uuid__")
         code.code = 1122
         old_json = code.to_json()
@@ -110,7 +111,7 @@ def test_save(self, access_code_json):
         assert code.name == "New name"
 
     def test_delete(self, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         code = AccessCode.from_json(auth, access_code_json, "__device_uuid__")
         auth.request.return_value = mock.Mock()
         code.delete()
diff --git a/tests/test_lock.py b/tests/test_lock.py
index c8e6ac5..b79cd20 100644
--- a/tests/test_lock.py
+++ b/tests/test_lock.py
@@ -3,13 +3,14 @@
 from unittest import mock
 
 import pyschlage
+from pyschlage.auth import Auth
 from pyschlage.code import AccessCode
 from pyschlage.lock import Lock
 
 
 class TestLock:
     def test_from_json(self, lock_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         lock = Lock.from_json(auth, lock_json)
         assert lock._auth == auth
         assert lock.device_id == "__wifi_uuid__"
@@ -23,14 +24,14 @@ def test_from_json(self, lock_json):
         assert lock.firmware_version == "10.00.00264232"
 
     def test_from_json_is_jammed(self, lock_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         lock_json["attributes"]["lockState"] = 2
         lock = Lock.from_json(auth, lock_json)
         assert not lock.is_locked
         assert lock.is_jammed
 
     def test_refresh(self, lock_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         lock = Lock.from_json(auth, lock_json)
         lock_json["name"] = "<NAME>"
 
@@ -41,7 +42,7 @@ def test_refresh(self, lock_json):
         assert lock.name == "<NAME>"
 
     def test_lock_wifi(self, wifi_lock_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         initial_json = deepcopy(wifi_lock_json)
         initial_json["attributes"]["lockState"] = 0
         lock = Lock.from_json(auth, initial_json)
@@ -58,7 +59,7 @@ def test_lock_wifi(self, wifi_lock_json):
         assert lock.is_locked
 
     def test_unlock_wifi(self, wifi_lock_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         initial_json = deepcopy(wifi_lock_json)
         initial_json["attributes"]["lockState"] = 1
         lock = Lock.from_json(auth, initial_json)
@@ -75,7 +76,7 @@ def test_unlock_wifi(self, wifi_lock_json):
         assert not lock.is_locked
 
     def test_lock_ble(self, ble_lock_json):
-        auth = mock.Mock(user_id="<user-id>")
+        auth = mock.create_autospec(Auth, spec_set=True, user_id="<user-id>")
         lock = Lock.from_json(auth, ble_lock_json)
         lock.lock()
 
@@ -94,7 +95,7 @@ def test_lock_ble(self, ble_lock_json):
         assert lock.is_locked
 
     def test_unlock_ble(self, ble_lock_json):
-        auth = mock.Mock(user_id="<user-id>")
+        auth = mock.create_autospec(Auth, spec_set=True, user_id="<user-id>")
         lock = Lock.from_json(auth, ble_lock_json)
         lock.unlock()
 
@@ -113,7 +114,7 @@ def test_unlock_ble(self, ble_lock_json):
         assert not lock.is_locked
 
     def test_access_codes(self, lock_json, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         lock = Lock.from_json(auth, lock_json)
 
         auth.request.return_value = mock.Mock(
@@ -127,7 +128,7 @@ def test_access_codes(self, lock_json, access_code_json):
         assert codes == [AccessCode.from_json(auth, access_code_json, lock.device_id)]
 
     def test_add_access_code(self, lock_json, access_code_json):
-        auth = mock.Mock()
+        auth = mock.create_autospec(Auth, spec_set=True)
         lock = Lock.from_json(auth, lock_json)
         code = AccessCode.from_json(auth, access_code_json, lock.device_id)
         # Users should not set these.