slightly better

shared_example.rb

RSpec.shared_examples "remember token" do
  describe '#remember_token' do
    subject { super().remember_token }
    it { is_expected.not_to be_blank }
  end
end

spec1.rb

  before do
    @admin = User.create(username: "user", password: "password", password_confirmation: "password")
  end

  subject{ @admin }

  include_examples "remember token"  

spec2.rb

  before do
    @admin = ApiUser.create(username: "user", password: "password", password_confirmation: "password")
  end

  subject{ @admin }

  include_examples "remember token"