diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e710138f..b8e6eb58 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -81,6 +81,7 @@ jobs:
             POSTGRES_CAS_PASS:${{ vars.GOOGLE_CLOUD_PROJECT }}/POSTGRES_CAS_PASS
             POSTGRES_CUSTOMER_CAS_CONNECTION_NAME:${{ vars.GOOGLE_CLOUD_PROJECT }}/POSTGRES_CUSTOMER_CAS_CONNECTION_NAME
             POSTGRES_CUSTOMER_CAS_PASS:${{ vars.GOOGLE_CLOUD_PROJECT }}/POSTGRES_CUSTOMER_CAS_PASS
+            POSTGRES_CUSTOMER_CAS_PASS_VALID_DOMAIN_NAME:${{ vars.GOOGLE_CLOUD_PROJECT }}/POSTGRES_CUSTOMER_CAS_PASS_VALID_DOMAIN_NAME
             SQLSERVER_CONNECTION_NAME:${{ vars.GOOGLE_CLOUD_PROJECT }}/SQLSERVER_CONNECTION_NAME
             SQLSERVER_USER:${{ vars.GOOGLE_CLOUD_PROJECT }}/SQLSERVER_USER
             SQLSERVER_PASS:${{ vars.GOOGLE_CLOUD_PROJECT }}/SQLSERVER_PASS
@@ -102,6 +103,7 @@ jobs:
           POSTGRES_CAS_PASS: "${{ steps.secrets.outputs.POSTGRES_CAS_PASS }}"
           POSTGRES_CUSTOMER_CAS_CONNECTION_NAME: "${{ steps.secrets.outputs.POSTGRES_CUSTOMER_CAS_CONNECTION_NAME }}"
           POSTGRES_CUSTOMER_CAS_PASS: "${{ steps.secrets.outputs.POSTGRES_CUSTOMER_CAS_PASS }}"
+          POSTGRES_CUSTOMER_CAS_PASS_VALID_DOMAIN_NAME: "${{ steps.secrets.outputs.POSTGRES_CUSTOMER_CAS_PASS_VALID_DOMAIN_NAME }}"
           SQLSERVER_CONNECTION_NAME: "${{ steps.secrets.outputs.SQLSERVER_CONNECTION_NAME }}"
           SQLSERVER_USER: "${{ steps.secrets.outputs.SQLSERVER_USER }}"
           SQLSERVER_PASS: "${{ steps.secrets.outputs.SQLSERVER_PASS }}"
diff --git a/tests/system/test_asyncpg_connection.py b/tests/system/test_asyncpg_connection.py
index 8de14d57..dfcc3941 100644
--- a/tests/system/test_asyncpg_connection.py
+++ b/tests/system/test_asyncpg_connection.py
@@ -16,13 +16,15 @@
 
 import asyncio
 import os
-from typing import Any
+from typing import Any, Union
 
 import asyncpg
 import sqlalchemy
 import sqlalchemy.ext.asyncio
 
 from google.cloud.sql.connector import Connector
+from google.cloud.sql.connector import DefaultResolver
+from google.cloud.sql.connector import DnsResolver
 
 
 async def create_sqlalchemy_engine(
@@ -31,6 +33,7 @@ async def create_sqlalchemy_engine(
     password: str,
     db: str,
     refresh_strategy: str = "background",
+    resolver: Union[type[DefaultResolver], type[DnsResolver]] = DefaultResolver,
 ) -> tuple[sqlalchemy.ext.asyncio.engine.AsyncEngine, Connector]:
     """Creates a connection pool for a Cloud SQL instance and returns the pool
     and the connector. Callers are responsible for closing the pool and the
@@ -64,9 +67,16 @@ async def create_sqlalchemy_engine(
             Refresh strategy for the Cloud SQL Connector. Can be one of "lazy"
             or "background". For serverless environments use "lazy" to avoid
             errors resulting from CPU being throttled.
+        resolver (Optional[google.cloud.sql.connector.DefaultResolver]):
+            Resolver class for resolving instance connection name. Use
+            google.cloud.sql.connector.DnsResolver when resolving DNS domain
+            names or google.cloud.sql.connector.DefaultResolver for regular
+            instance connection names ("my-project:my-region:my-instance").
     """
     loop = asyncio.get_running_loop()
-    connector = Connector(loop=loop, refresh_strategy=refresh_strategy)
+    connector = Connector(
+        loop=loop, refresh_strategy=refresh_strategy, resolver=resolver
+    )
 
     async def getconn() -> asyncpg.Connection:
         conn: asyncpg.Connection = await connector.connect_async(
@@ -183,6 +193,24 @@ async def test_lazy_sqlalchemy_connection_with_asyncpg() -> None:
     await connector.close_async()
 
 
+async def test_custom_SAN_with_dns_sqlalchemy_connection_with_asyncpg() -> None:
+    """Basic test to get time from database."""
+    inst_conn_name = os.environ["POSTGRES_CUSTOMER_CAS_PASS_VALID_DOMAIN_NAME"]
+    user = os.environ["POSTGRES_USER"]
+    password = os.environ["POSTGRES_CUSTOMER_CAS_PASS"]
+    db = os.environ["POSTGRES_DB"]
+
+    pool, connector = await create_sqlalchemy_engine(
+        inst_conn_name, user, password, db, resolver=DnsResolver
+    )
+
+    async with pool.connect() as conn:
+        res = (await conn.execute(sqlalchemy.text("SELECT 1"))).fetchone()
+        assert res[0] == 1
+
+    await connector.close_async()
+
+
 async def test_connection_with_asyncpg() -> None:
     """Basic test to get time from database."""
     inst_conn_name = os.environ["POSTGRES_CONNECTION_NAME"]
diff --git a/tests/system/test_pg8000_connection.py b/tests/system/test_pg8000_connection.py
index b56a8e82..c47b860c 100644
--- a/tests/system/test_pg8000_connection.py
+++ b/tests/system/test_pg8000_connection.py
@@ -18,10 +18,14 @@
 import os
 
 # [START cloud_sql_connector_postgres_pg8000]
+from typing import Union
+
 import pg8000
 import sqlalchemy
 
 from google.cloud.sql.connector import Connector
+from google.cloud.sql.connector import DefaultResolver
+from google.cloud.sql.connector import DnsResolver
 
 
 def create_sqlalchemy_engine(
@@ -30,6 +34,7 @@ def create_sqlalchemy_engine(
     password: str,
     db: str,
     refresh_strategy: str = "background",
+    resolver: Union[type[DefaultResolver], type[DnsResolver]] = DefaultResolver,
 ) -> tuple[sqlalchemy.engine.Engine, Connector]:
     """Creates a connection pool for a Cloud SQL instance and returns the pool
     and the connector. Callers are responsible for closing the pool and the
@@ -64,8 +69,13 @@ def create_sqlalchemy_engine(
             Refresh strategy for the Cloud SQL Connector. Can be one of "lazy"
             or "background". For serverless environments use "lazy" to avoid
             errors resulting from CPU being throttled.
+        resolver (Optional[google.cloud.sql.connector.DefaultResolver]):
+            Resolver class for resolving instance connection name. Use
+            google.cloud.sql.connector.DnsResolver when resolving DNS domain
+            names or google.cloud.sql.connector.DefaultResolver for regular
+            instance connection names ("my-project:my-region:my-instance").
     """
-    connector = Connector(refresh_strategy=refresh_strategy)
+    connector = Connector(refresh_strategy=refresh_strategy, resolver=resolver)
 
     def getconn() -> pg8000.dbapi.Connection:
         conn: pg8000.dbapi.Connection = connector.connect(
@@ -153,3 +163,21 @@ def test_customer_managed_CAS_pg8000_connection() -> None:
         curr_time = time[0]
         assert type(curr_time) is datetime
     connector.close()
+
+
+def test_custom_SAN_with_dns_pg8000_connection() -> None:
+    """Basic test to get time from database."""
+    inst_conn_name = os.environ["POSTGRES_CUSTOMER_CAS_PASS_VALID_DOMAIN_NAME"]
+    user = os.environ["POSTGRES_USER"]
+    password = os.environ["POSTGRES_CUSTOMER_CAS_PASS"]
+    db = os.environ["POSTGRES_DB"]
+
+    engine, connector = create_sqlalchemy_engine(
+        inst_conn_name, user, password, db, resolver=DnsResolver
+    )
+    with engine.connect() as conn:
+        time = conn.execute(sqlalchemy.text("SELECT NOW()")).fetchone()
+        conn.commit()
+        curr_time = time[0]
+        assert type(curr_time) is datetime
+    connector.close()