old_contents: const should = require('should');
  
  module.exports = (response, additionalProps = []) => {
    should(response).have.properties('access_token', 'expires_in', ...additionalProps);
    should(response.token_type).be.eql('Bearer');
  };
  
new_contents: const should = require('should');
  
  module.exports = (response, additionalProps = []) => {
    should(response).have.properties('access_token', 'expires_in', ...additionalProps);
    should(response.token_type).be.eql('Bearer');
    should(response.access_token.length).be.greaterThan(15);
    should(response.refresh_token.length).be.greaterThan(15);
  };
  
subject: Add other checks