关于if xx.save的问题

比如 有这样一个方法：

def create
    @itouch_service = ItouchService.new(params[:itouch_service])
    @member = Member.find(session[:member_id])
    @itouch_service.member = @member
    respond_to do |format|
     if @itouch_service.save
        flash[:notice] = 'ItouchService was successfully created.'
        format.html { redirect_to(new_service_logo_path(@itouch_service)) }
        format.xml  { render :xml => @itouch_service, :status => :created, :location => @itouch_service }
       else
        format.html { render :action => "new" }
        format.xml  { render :xml => @itouch_service.errors, :status => :unprocessable_entity }
      end
    end
  end

我测试它的时候写的方法是：

 def test_create
    liwan=members(:liwan_member )
    post :create,{:itouch_service=>{:provider_type=>'Member',:provider_id=>1}},{:member_id=>liwan.id}
    assert_response :redirect
    assert_redirected_to :action=>'new_service_logo'
  end

但是报错， Expected response to be a <:redirect>,but was <200>
意思就是测试的方法并没有保存成功！所以不会重定向！但是我把这句 if @itouch_service.save中的 if去掉，把方法改为：

  def create
    @itouch_service = ItouchService.new(params[:itouch_service])
    @member = Member.find(session[:member_id])
    @itouch_service.member = @member
    @itouch_service.save
    respond_to do |format|
        flash[:notice] = 'ItouchService was successfully created.'
        format.html { redirect_to(new_service_logo_path(@itouch_service)) }
        format.xml  { render :xml => @itouch_service, :status => :created, :location => @itouch_service }
    end
  end

这样就好了，测试成功！不知道是不是if的原因还是我写的测试有问题的原因！请帮忙看以下！