Add test case

Author: abowden1989

pandas/tests/io/test_sql.py

@@ -1527,6 +1527,20 @@ def test_con_string_import_error(self):
         with pytest.raises(ImportError, match="SQLAlchemy"):
             sql.read_sql("SELECT * FROM iris", conn)
 
+    @pytest.mark.skipif(SQLALCHEMY_INSTALLED, reason="SQLAlchemy is installed")
+    def test_con_unknown_dbapi2_class_does_not_error_without_sql_alchemy_installed(
+        self,
+    ):
+        class MockSqliteConnection:
+            def __init__(self, *args, **kwargs):
+                self.conn = sqlite3.Connection(*args, **kwargs)
+
+            def __getattr__(self, name):
+                return getattr(self.conn, name)
+
+        conn = MockSqliteConnection(":memory:")
+        sql.read_sql("SELECT 1", conn)
+
     def test_read_sql_delegate(self):
         iris_frame1 = sql.read_sql_query("SELECT * FROM iris", self.conn)
         iris_frame2 = sql.read_sql("SELECT * FROM iris", self.conn)