Example of how to use the strategy pattern in Ruby to create a fake and a real API client

dog_ceo_api.rb

require 'uri'
require 'json'
require 'net/http'

# https://dog.ceo/dog-api/
class DogCeoAPI
  class FakeStrategy
    def get_random
      {
        "message" => "https://images.dog.ceo/breeds/terrier-welsh/lucy.jpg",
        "status" => "success"
      }
    end
  end

  class ClientStrategy
    def get_random
      uri = URI('https://dog.ceo/api/breeds/image/random')

      response = Net::HTTP.get_response(uri)

      JSON.parse(response.body)
    end
  end

  def initialize(client:)
    @client = client.new
  end

  def get_random
    @client.get_random
  end
end

dog_ceo = DogCeoAPI.new(client: DogCeoAPI::FakeStrategy)
p dog_ceo.get_random


dog_ceo = DogCeoAPI.new(client: DogCeoAPI::ClientStrategy)
p dog_ceo.get_random