https://traversal.ist/how-to-fake-an-api - MapsAPI class

maps_api.rb

require 'json'

class MapsAPI

  def get_directions(origin, destination, real_request = false)
    response = api_endpoint(google_maps_api_key(real_request), origin, destination, real_request)
    parsed = JSON.parse(response)
    {
      'status': parsed['status'],
      'distance': parsed['routes'][0]['legs'][0]['distance']['value'].to_i,
      'duration': parsed['routes'][0]['legs'][0]['duration']['value'].to_i
    }
  end

  private

  def google_maps_api_key(real_request = false)
    if real_request
      Rails.application.credentials.google_maps[:api_key]
    else
      'FAKEKEY_FJ8302S93LAAZD'
    end
  end

  def api_endpoint(api_key, origin, destination, real_request = false)
    # If any of the fields are not provided
    if api_key == '' || origin == '' || destination == ''
      # return early with a status
      return JSON.generate({'status': 'BAD REQUEST'})
    end

    if real_request
      return RestClient.get("https://maps.googleapis.com/maps/api/directions/json?&origin=#{origin}&destination=#{destination}&key=#{api_key}")
    end

    # some code that returns what we want
    distance_value = 17981
    duration_value = 2404
    status = 'OK'

    # re-create the data structure of the API we're modeling.
    output_hash = {
      "geocoded_waypoints": [],
      "routes": [
        {"legs": [
          {
            "distance": {"value": distance_value},
            "duration": {"value": duration_value}
          }
        ]}
      ],
      "status": "OK"
    }

    JSON.generate(output_hash)
  end
end