curl_test.sh

$ curl -XGET -H "Content-Type: application/json" -H "Accept: application/json" "http://api.example.dev:13000/v1/echo/wibble"
{"message":"wibble"}%

rake_test.txt

$ rake test
Run options: --seed 12839

# Running:

F.

Finished in 0.035461s, 56.4000 runs/s, 56.4000 assertions/s.

  1) Failure:
API::V1::StatusControllerTest#test_echo_route [/.../test/controllers/api/v1/status_controller_test.rb:5]:
No route matches "/v1/echo/wibble"

2 runs, 2 assertions, 1 failures, 0 errors, 0 skips

routes.rb

Rails.application.routes.draw do

  namespace :api, :path => "", :constraints => { :subdomain => "api" }, :defaults => { :format => :json } do
    namespace :v1 do
      resources :users
      get '/echo/:message', to: 'status#echo'
    end
  end
end

routes.txt

$ rake routes                                                                                                   1 ↵
          Prefix Verb   URI Pattern                  Controller#Action
    api_v1_users GET    /v1/users(.:format)          api/v1/users#index {:format=>:json, :subdomain=>"api"}
                 POST   /v1/users(.:format)          api/v1/users#create {:format=>:json, :subdomain=>"api"}
 new_api_v1_user GET    /v1/users/new(.:format)      api/v1/users#new {:format=>:json, :subdomain=>"api"}
edit_api_v1_user GET    /v1/users/:id/edit(.:format) api/v1/users#edit {:format=>:json, :subdomain=>"api"}
     api_v1_user GET    /v1/users/:id(.:format)      api/v1/users#show {:format=>:json, :subdomain=>"api"}
                 PATCH  /v1/users/:id(.:format)      api/v1/users#update {:format=>:json, :subdomain=>"api"}
                 PUT    /v1/users/:id(.:format)      api/v1/users#update {:format=>:json, :subdomain=>"api"}
                 DELETE /v1/users/:id(.:format)      api/v1/users#destroy {:format=>:json, :subdomain=>"api"}
          api_v1 GET    /v1/echo/:message(.:format)  api/v1/status#echo {:format=>:json, :subdomain=>"api"}

status_controller.rb

class API::V1::StatusController < ApplicationController

  def echo
    respond_to do |format|
      format.json { render json: { :message => params[:message] } }
    end
  end
end

status_controller_test.rb

require 'test_helper'

class API::V1::StatusControllerTest < ActionController::TestCase
  test "echo route" do
    assert_routing "http://api.example.dev/v1/echo/wibble", {
        :format => :json,
        :subdomain => "api",
        :controller => "api/v1/status",
        :action => "echo",
        :message => "wibble" }
  end

  test "should echo message" do
    get :echo, :message => 'wibble', :format => 'json'
    assert_response :success
    json = JSON.parse(@response.body)
    assert_equal "wibble", json["message"]
  end
end