RSPEC: How to test that a JSON Web Token is returned by controller action

I am using Devise and JWT's to authenticate users in a project I am writing. I am having a hard time figuring out how to write a useful test to expect a JWT response.body (since each is encrypted).

The only thing I can think of is to test that they are structured as a JWT should be (a 3 segment, '.' delimited string).

Has anyone encountered testing random/hashed returns and come up with a better solution?

describe SessionTokensController, type: :controller do
  let(:current_user) { FactoryGirl.create(:user) }

  before(:each) do
    sign_in current_user
  end

  describe '#create' do
    it 'responds with a JWT' do
      post :create
      token = JSON.parse(response.body)['token']

      expect(token).to be_kind_of(String)
      segments = token.split('.')
      expect(segments.size).to eql(3)
    end
  end
end

```