def METHOD_NAME(settings, requests_mock):
    settings.PLAIN_API = "https://api.plain.com/graphql/"
    requests_mock.post(
        settings.PLAIN_API,
        json={
            "data": {
                "upsertCustomer": {
                    "result": "UPDATED",
                    "customer": {"id": "c_ABC25904A1DA4E0A82934234F2"},
                    "error": None,
                }
            }
        },
    )
    customer_id = create_customer(
        {
            "id": "1",
            "name": "Ester",
            "fullname": "Ester",
            "email": "ester@example.com",
            "username": "",
        }
    )
    assert customer_id == "c_ABC25904A1DA4E0A82934234F2"