def METHOD_NAME(self):
    """
    ``install_optimal_reactor`` will use the default reactor if it is
    unable to detect the platform it is running on.
    """
    reactor_mock = Mock()
    self.patch_reactor("selectreactor", reactor_mock)
    self.patch(sys, "platform", "unknown")
    # Emulate that a reactor has not been installed
    self.patch_modules()
    choosereactor.install_optimal_reactor()
    reactor_mock.install.assert_called_once_with()