在 RSpec 中使用 shared examples

使用 RSpec 撰寫測試時，我們可以使用 shared examples 將常用的測試範例封裝起來，方便隨時調用。

假設我們撰寫了一些測試，如下

require "spec_helper"

describe VideosController do

  describe "GET index" do
    it "sets @categories for authenticated users" do
      set_current_user
      category = Fabricate(:category)
      get :index
      expect(assigns(:categories)).to eq [category]
    end

    it "redirects to the sign in page" do
      get :index
      expect(response).to redirect_to sign_in_path
    end

    it "sets the flash error message" do
      get :index
      expect(flash[:error]).to be_present
    end

  end

  describe "GET show" do
    it "sets @video for authenticated user" do
      set_current_user
      video = Fabricate(:video)
      get :show, id: video.slug
      expect(assigns(:video)).to eq video
    end

    it "redirects to the sign in page" do
      video = Fabricate(:video)
      get :show, id: video.slug
      expect(response).to redirect_to sign_in_path
    end

    it "sets the flash error message" do
      video = Fabricate(:video)
      get :show, id: video.slug
      expect(flash[:error]).to be_present
    end

  end

end

正如所見，GET index 和 GET show 裡面存在著類似的測試，我們可以此部分放到 spec/support/shared_examples.rb 裡面

shared_examples "requires sign in" do

  it "redirects to the sign in page" do
    action
    expect(response).to redirect_to sign_in_path
  end

  it "sets the flash error message" do
    action
    expect(flash[:error]).to be_present
  end

end

於是原先的測試程式就可以 refactor 成

require "spec_helper"

describe VideosController do

  describe "GET index" do
    it "sets @categories for authenticated users" do
      set_current_user
      category = Fabricate(:category)
      get :index
      expect(assigns(:categories)).to eq [category]
    end

    it_behaves_like "requires sign in" do
      video = Fabricate(:video)
      let(:action) { get :index }
    end

  end

  describe "GET show" do
    it "sets @video for authenticated user" do
      set_current_user
      video = Fabricate(:video)
      get :show, id: video.slug
      expect(assigns(:video)).to eq video
    end

    it_behaves_like "requires sign in" do
      video = Fabricate(:video)
      let(:action) { get :show, id: video.slug }
    end

  end

end

除了程式碼變得簡潔之外，日後我們也更容易對封裝的部分進行功能的擴充或修改。

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在 RSpec 中使用 shared examples

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