ruby-on-rails – RSpec：如何测试从控制器调用私有帮助器方法的

一个应用程序助手方法,从中调用控制器助手方法(私有).

码：

ApplicationHelper：

def ordenar(coluna,titulo = nil)  
    titulo ||= coluna.titleize  
    css_class = (coluna == **coluna_ordenacao**) ? "#{**direcao_ordenacao**}" : "ordenavel"  
    direcao = (coluna == **coluna_ordenacao** and **direcao_ordenacao** == "asc") ? :desc : :asc  
    link_to titulo,{:sort => coluna,:direction => direcao},{:class => css_class}  
end

ApplicationController中：

helper_method :coluna_ordenacao,:direcao_ordenacao  
private  
def coluna_ordenacao  
    return params[:sort] if params[:sort] and params[:sort].split(' ').size == 1  
    return :created_at  
end  

def direcao_ordenacao  
    return %w[asc desc].include?(params[:direction]) ? params[:direction] : :desc  
end

这是问题：无法从RSpec调用coluna_ordenacao和direcao_ordenacao方法,它给出了以下错误：

undefined local variable or method `coluna_ordenacao' for #<RSpec::Core::ExampleGroup::Nested_1::Nested_2:0x7fbf0a9fe3d8>

有没有办法让它起作用？顺便说一下,我正在测试助手,而不是控制器