def METHOD_NAME(
    staff_api_client, customer_user, permission_manage_users
):
    # given
    query = CUSTOMER_DELETE_MUTATION
    variables = {"externalReference": "whatever", "id": "whatever"}
    # when
    response = staff_api_client.post_graphql(
        query, variables, permissions=[permission_manage_users]
    )
    content = get_graphql_content(response)
    # then
    errors = content["data"]["customerDelete"]["errors"]
    assert (
        errors[0]["message"]
        == "Argument 'id' cannot be combined with 'external_reference'"
    )