UI2API

As more web applications make use of an interface to interact with their service layer, people now have more flexibility to set up and verify parts of their UI tests without needing to use a browser.

This simple gem makes it easy to subclass UI2API::Base and provide all of the information necessary to interact with the different REST endpoints available in your application.

This code is designed to be used with the watir_model gem. The Model stores data in a way that makes it easy to compare the input and output from both the API and the UI.

Note that while this gem can be used as the basis of an API Testing suite, its primary focus is on comparing input and output from UI to API and back.

Add this line to your application's Gemfile:

gem 'ui2api'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ui2api

1. Set the base url

   UI2API::Base.base_url = 'https://restful-booker.herokuapp.com'

2. Create a subclass with an endpoint:

   module API
     class Booking < UI2API::Base
       def self.endpoint
         'booking'
       end
     end
   end

3. Make API calls

   booking = {firstname: 'Trey',
              lastname: 'Ruecker',
              totalprice: 83,
              depositpaid: true,
              bookingdates: {checkin: '3/23/2019',
                             checkout: '3/27/2019'}}
    
   API::Booking.create(booking)

4. The Array or Hash of results is accessed with #data

   booking = {firstname: 'David',
              lastname: 'Jones',
              totalprice: 183,
              depositpaid: true,
              bookingdates: {checkin: '3/23/2019',
                             checkout: '3/27/2019'}}
    
   created_booking = API::Booking.create(booking)
   booking_id = created_booking.data[:bookingid]
    
   stored_booking = API::Booking.show(id: booking_id).data
    
   expect(stored_booking).to eq booking

5. Use Watir Model

   Note that the code in the previous example will actually fail. This is because we are storing dates as String values and the input String does not match the output String

   Hashes are hard to compare, which is why we have WatirModel. WatirModel is designed to store the canonical representation of related data in the appropriate data type, specifically so that data can be correctly compared.

   module Model
     class BookingDates < WatirModel
       key(:checkin, data_type: Date) { Faker::Date.forward }
       key(:checkout, data_type: Date) { checkin + 4 }
     end
    
     class Booking < WatirModel
       key(:firstname) { Faker::Name.first_name }
       key(:lastname) { Faker::Name.last_name }
       key(:totalprice, data_type: Integer) { Faker::Commerce.price.round }
       key(:depositpaid) { true }
       key(:bookingdates, data_type: BookingDates) { BookingDates.new }
       key(:additionalneeds)
     end
   end

   Because we have a model class defined that is named the same as the API class, UI2API will automatically attempt to create an instance of the model from the return value of the API call. It is accessible from a method based on the name of the API/Model classes, so in this case #booking:

   booking = Model::Booking.new
    
   created_booking = API::Booking.create(booking)
   booking_id = created_booking.data[:bookingid]
    
   stored_booking = API::Booking.show(id: booking_id).booking
    
   expect(stored_booking).to eq booking

6. Customize

   You have a subclass, so if you need to add or change things before or after a call, just override the UI2API method in your subclass:

   module API
     class Booking < UI2API::Base
     
       attr_reader :id
       
       def initialize(*)
         super
         return if @data.is_a?(Array)
         @id = @data[:bookingid]
       end
     end
   end

   Now we can use this like so:

   booking = Model::Booking.new
    
   created_booking = API::Booking.create(booking)
    
   expect(created_booking.id).to eq created_booking.data[:bookingid]

   Because this pattern comes in very handy, you can use #define_attribute to do the same thing:

   module API
     class Booking < UI2API::Base
       def initialize(*)
         super
         return if @data.is_a?(Array)
         define_attribute(:id, @data[:bookingid])
       end
     end
   end

Bug reports and pull requests are welcome on GitHub at https://github.com/titusfortner/ui2api.

While I've been leveraging this approach at my past few jobs, my solutions were application specific and <cough> not satisfyingly elegant. My initial attempts at implementing this gem were much too over-engineered and weren't solving the actual general use case, so this project has stayed on the shelf in spite of the industry need for it. Then at the 2017 Selenium Conference in Berlin, Mark Winteringham gave a talk titled REST APIs and WebDriver: In Perfect Harmony. This gave me the outside vantage point I needed to see how to focus the project. I started by copying the functionality of the code in Mark's repo, and then added in some extra goodness that leveraging WatirModel provides.

The gem is available as open source under the terms of the MIT License.