attachments_controller_spec.rb

require 'rails_helper'

RSpec.describe AttachmentsController, type: :controller do

  let!(:question) { create(:question) }
  let!(:answer2) { create(:answer, question: question) }

  describe 'DELETE #destroy' do
    sign_in_user
    let!(:answer)  { create(:answer, question: question, user: @user) }
    let!(:attachment) { create(:attachment) }
    context 'answer of author' do

      it "deletes author's attachment" do
        expect { delete :destroy, params: { id: attachment.id, format: :js }  }.to change(Attachment, :count).by(-1)
      end

      it 'renders destroy template' do
        delete :destroy, params: { id: attachment, format: :js }
        expect(response).to render_template :destroy
      end
    end