Grape with a route param.rb

require 'grape'

class API < Grape::API
  prefix :api
  version 'v1', using: :path

  resources :users do
    desc 'return all users'
    get '/' do
      puts 'Users'
    end

    desc 'returns a user'
    params do
      requires :id, type: Integer
    end
    get ':id' do
      puts "User: #{params[:id]}"
    end
  end
end

options = {
  method: 'GET'
}

env = Rack::MockRequest.env_for('/api/v1/users/12', options)
API.call env