RSpec + 表单对象 + 简单表单给出未定义的方法

我正在尝试对控制器的规范进行一些嘲笑。当我发布有效文章时，我已经编写了适用于这种情况的代码，但是当我尝试指定不应保存它时，我遇到了错误。

我的代码：

文章形式：

class ArticleForm
  include ActiveModel::Model
  delegate :title, :body, :author_id, :tags, :id, :persisted?, :new_record?, to: :article
  attr_accessor :article, :tags_string
  validates :title, :body, :tags, presence: true
  validates_length_of :title, within: 8..512
  validates_length_of :body, within: 8..2048
  validate :validate_prohibited_words

  def initialize(article = Article.new)
    @article = article
  end

  def save(article_params)
    assign_params_to_article(article_params)

    if valid?
      @article.tags.each(&:save!)
      @article.save!
      true
    else
      false
    end
  end
...
end

文章控制器（仅创建操作）：

  def create
    @article_form = ArticleForm.new
    if @article_form.save(article_params)
      flash[:notice] = 'You have added a new article.'
      redirect_to @article_form.article
    else
      flash[:danger] = 'Failed to add new article.'
      render :new
    end
  end

_形式：

= simple_form_for @article_form,
  url: (@article_form.article.new_record? ? articles_path : article_path(@article_form.article) ) do |f|
  = f.input :title, label: "Article title:"
  = f.input :body, label: "Body of the article:", as: :text, input_html: { :style => 'height: 200px' }
  = f.input :tags_string, label: "Tags:", input_html: { value: f.object.all_tags }
  = f.button :submit, 'Send!'

文章控制器规格：

require 'rails_helper'

RSpec.describe ArticlesController, type: :controller do
  render_views

  let!(:user) { create(:user) }
  let!(:tag) { create(:tag) }
  let(:tags_string) { 'test tag' }
  let!(:article) { create(:article, :with_comments, tags: [tag], author_id: user.id) }


  context 'user logged in' do
    before { sign_in(user) }

    describe 'POST artictles#create' do
      let(:article_form) { instance_double(ArticleForm) }
      let(:form_params) do
        {
          article_form:
          {
            title: 'title',
            body: 'body',
            tags_string: tags_string
          }
        }
      end

      context 'user adds valid article' do
        it 'redirects to new article', :aggregate_failures do
          expect(ArticleForm).to receive(:new).and_return(article_form)
          expect(article_form).to receive(:save).with(hash_including(:author_id, form_params[:article_form]))
                                                .and_return(true)
          allow(article_form).to receive(:article) { article }

          post :create, params: form_params
          expect(response).to redirect_to(article)
        end
      end

      context 'user adds invalid article' do
        it 'renders new form', :aggregate_failures do
          expect(ArticleForm).to receive(:new).and_return(article_form)
          allow(article_form).to receive(:article) { article }

          expect(article_form).to receive(:save).with(hash_including(:author_id, form_params[:article_form]))
                                                .and_return(false)

          post :create, params: form_params
          expect(response).to render_template(:new)
        end
      end
    end
  end
end

发布有效工作正常，这是我在“无效帖子”上得到的错误：

失败：

1) ArticlesController 用户登录 POST 文章#create 用户添加无效文章呈现新表单 出现 1 个失败和 1 个其他错误：

 1.1) Failure/Error: = simple_form_for @article_form,
        #<InstanceDouble(ArticleForm) (anonymous)> received unexpected message :model_name with (no args)
      # ./app/views/articles/_form.html.haml:2:in `_app_views_articles__form_html_haml__2443549359101958040_47338976410880'
      # ./app/views/articles/new.html.haml:2:in `_app_views_articles_new_html_haml___678894721646621807_47338976253400'
      # ./app/controllers/articles_controller.rb:26:in `create'
      # ./spec/controllers/articles_controller_spec.rb:51:in `block (5 levels) in <top (required)>'

 1.2) Failure/Error: = simple_form_for @article_form,

      ActionView::Template::Error:
        undefined method `param_key' for #<Array:0x0000561bedbcd888>
      # ./app/views/articles/_form.html.haml:2:in `_app_views_articles__form_html_haml__2443549359101958040_47338976410880'
      # ./app/views/articles/new.html.haml:2:in `_app_views_articles_new_html_haml___678894721646621807_47338976253400'
      # ./app/controllers/articles_controller.rb:26:in `create'
      # ./spec/controllers/articles_controller_spec.rb:51:in `block (5 levels) in <top (required)>'
      # ------------------
      # --- Caused by: ---
      # NoMethodError:
      #   undefined method `param_key' for #<Array:0x0000561bedbcd888>
      #   ./app/views/articles/_form.html.haml:2:in `_app_views_articles__form_html_haml__2443549359101958040_47338976410880'

我很少尝试通过允许对象接收它来添加缺少的方法，但这是一件好事吗？以后我必须允许每次调用（当我允许 param_keys 时，它会询问 _form 的所有值 - 标题、正文和标签）。有没有办法让它在不逐行指定所有方法的情况下工作？