diff --git a/google/cloud/alloydb/connector/instance.py b/google/cloud/alloydb/connector/instance.py
index 06f3c17..40b2d77 100644
--- a/google/cloud/alloydb/connector/instance.py
+++ b/google/cloud/alloydb/connector/instance.py
@@ -39,7 +39,7 @@
 )
 
 
-def parse_instance_uri(instance_uri: str) -> Tuple[str, str, str, str]:
+def _parse_instance_uri(instance_uri: str) -> Tuple[str, str, str, str]:
     # should take form "projects/<PROJECT>/locations/<REGION>/clusters/<CLUSTER>/instances/<INSTANCE>"
     if INSTANCE_URI_REGEX.fullmatch(instance_uri) is None:
         raise ValueError(
@@ -47,9 +47,7 @@ def parse_instance_uri(instance_uri: str) -> Tuple[str, str, str, str]:
             "format: projects/<PROJECT>/locations/<REGION>/clusters/<CLUSTER>/instances/<INSTANCE>, projects/<DOMAIN>:<PROJECT>/locations/<REGION>/clusters/<CLUSTER>/instances/<INSTANCE>"
             f"got {instance_uri}."
         )
-
     instance_uri_split = INSTANCE_URI_REGEX.split(instance_uri)
-
     return (
         instance_uri_split[1],
         instance_uri_split[3],
@@ -79,17 +77,15 @@ def __init__(
         client: AlloyDBClient,
         keys: asyncio.Future[Tuple[rsa.RSAPrivateKey, str]],
     ) -> None:
-
-        self._instance_uri = instance_uri
-
         # validate and parse instance_uri
         (
             self._project,
             self._region,
             self._cluster,
             self._name,
-        ) = parse_instance_uri(instance_uri)
+        ) = _parse_instance_uri(instance_uri)
 
+        self._instance_uri = instance_uri
         self._client = client
         self._keys = keys
         self._refresh_rate_limiter = AsyncRateLimiter(
diff --git a/tests/unit/test_instance.py b/tests/unit/test_instance.py
index 7970d9c..2a76169 100644
--- a/tests/unit/test_instance.py
+++ b/tests/unit/test_instance.py
@@ -14,36 +14,50 @@
 
 import asyncio
 from datetime import datetime, timedelta
+from typing import Tuple
 
 import aiohttp
 from mocks import FakeAlloyDBClient
 import pytest
 
 from google.cloud.alloydb.connector.exceptions import RefreshError
-from google.cloud.alloydb.connector.instance import Instance, parse_instance_uri
+from google.cloud.alloydb.connector.instance import _parse_instance_uri, Instance
 from google.cloud.alloydb.connector.refresh import _is_valid, RefreshResult
 from google.cloud.alloydb.connector.utils import generate_keys
 
 
-@pytest.mark.asycio
-async def test_parser_instance_uri() -> None:
+@pytest.mark.parametrize(
+    "instance_uri, expected",
+    [
+        (
+            "projects/test-project/locations/test-region/clusters/test-cluster/instances/test-instance",
+            ("test-project", "test-region", "test-cluster", "test-instance"),
+        ),
+        (
+            "projects/test-domain:test-project/locations/test-region/clusters/test-cluster/instances/test-instance",
+            (
+                "test-domain:test-project",
+                "test-region",
+                "test-cluster",
+                "test-instance",
+            ),
+        ),
+    ],
+)
+def test_parse_instance_uri(instance_uri: str, expected: Tuple[str, str, str]) -> None:
     """
-    Test to check whether the __init__ method of Instance
-    can tell if the instance URI that's passed in is formatted correctly.
+    Test that _parse_instance_uri correctly on
+    normal instance uri and domain-scoped projects.
     """
-    instance_uri = [
-        "projects/test-project/locations/test-region/clusters/test-cluster/instances/test-instance",
-        "projects/google.com:test-project/locations/test-region/clusters/test-cluster/instances/test-instance",
-    ]
+    assert expected == _parse_instance_uri(instance_uri)
 
-    for uri in instance_uri:
-        project, region, cluster, name = parse_instance_uri(uri)
-        assert (
-            project in ["test-project", "google.com:test-project"]
-            and region == "test-region"
-            and cluster == "test-cluster"
-            and name == "test-instance"
-        )
+
+def test_parse_bad_instance_uri() -> None:
+    """
+    Tests that ValueError is thrown for bad instance uri.
+    """
+    with pytest.raises(ValueError):
+        _parse_instance_uri("test-project:test-instance")
 
 
 @pytest.mark.asyncio