def METHOD_NAME(cls, extras=None):
    """Application settings to be used. Override to tweak default settings
    for the tests.
    :param dict extras: extra settings values
    :rtype: dict
    """
    settings = {**DEFAULT_SETTINGS}
    settings["storage_backend"] = "kinto.core.storage.memory"
    settings["cache_backend"] = "kinto.core.cache.memory"
    settings["permission_backend"] = "kinto.core.permission.memory"
    settings.update(extras or None)
    return settings