some_controller.rb

require 'spec_helper'

describe ConferenceController do
  let(:user) { create(:user) }

  describe 'testing user' do
    it 'checks for admin user' do
      expect(user.is_admin).to be_falsey
      sign_in user
      expect(controller.current_user).to be_truthy
    end
  end
end

describe ConferenceController do
  let(:user) { create(:user) }
  let(:admin) { create(:admin) }

  describe 'testing user' do
    it 'checks for admin user' do
      expect(user.is_admin).to eq(false)
      sign_in user
      expect(controller.current_user.is_admin).to eq(false)
    end
  end
  describe 'testing admin' do
    it 'checks for admin user' do
      expect(admin.is_admin).to eq(true)
      sign_in admin
      expect(controller.current_user.is_admin).to eq(true)
    end
  end
end