test: add explicit credentials and project to test

Tests need to be able to run in environments without any default credentials.
This requires the test to explictly set the credentials and the project that
should be used.

Author: olavloite

tests/unit/spanner_dbapi/test_connection.py

@@ -830,7 +830,14 @@ def test_custom_database_role(self):
         from google.cloud.spanner_dbapi import connect
 
         role = "some_role"
-        connection = connect("test-instance", "test-database", database_role=role)
+        connection = connect(
+            "test-instance",
+            "test-database",
+            project="test-project",
+            database_role=role,
+            credentials=AnonymousCredentials(),
+            client_options={"api_endpoint": "none"},
+        )
         self.assertEqual(connection.database.database_role, role)
 
     def test_invalid_custom_client_connection(self):