How To Mock Endpoints in Automated Acceptance Tests

The purpose of acceptance testing is to reproduce production environment as much as possible in order to evaluate the software in a ‘real-world’ situation similar to what the customers will experience and this includes using real endpoints.

But using real endpoints has some disadvantages. In automated acceptance tests, the endpoint will be stressed out and this is not performance testing. Also, you must use production data (even usernames and passwords) and this is not good because you might break something there. The list with the reasons could go on and on and this is why you should mock some endpoints in automated acceptance tests. Also, you should keep your endpoint’s URL stored in environment variables to be able to change it easily (production URL or mock URL).

I will show you some basic examples of mocking endpoints written in Ruby, Python and GO.

Mock endpoint in Ruby

I have used Sinatra (DSL for quickly creating web applications in Ruby) which is very easy to use.

Install the gem:

gem install sinatra

#myapp.rb

require ‘json’
require ‘sinatra’

get '/:username' do
  if params[:username] != 'your_username'
  	status 404
  else
  	content_type :json
  	{'message' => 'success'}.to_json
  end
end

ruby myapp.rb -o 0.0.0.0 -p 5000 > /dev/null 2>&1 &

This will start the process in background and your endpoint on http://localhost:5000.

If you make a GET request on http://localhost:5000/your_username you will get a ‘success’ message, else a 404 status code.

Mock endpoint in Python

In Python it is very easy to create an endpoint with Flask.

To install it you have to run:

pip install flask-restful

#myapp.py

#!flask/bin/python
from flask import Flask, jsonify
from flask import Response
import json

app = Flask(__name__)

@app.route("/<username>", methods=['GET'])
def put_username(username):
    if username == 'your_username':
        resp = Response("success!\n", mimetype='application/json')
    else:
        resp = Response("", status=404, mimetype='application/json')

    return resp

if __name__ == '__main__':
    app.run(debug=True)

As you can see, this does the exact same thing as the endpoint created in Ruby.

You simply run it with

python myapp.py

Mock endpoint in GO

//myapp.go
package main

import (
	"fmt"
	"net/http"
	"github.com/julienschmidt/httprouter"
)

func username(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
	if p.ByName("username") == "your_username" {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(200)
		fmt.Fprint(w, `{"message":"success"}`)
	} else {
		w.WriteHeader(404)
	}
}

func main() {
	r := httprouter.New()
	r.GET("/:username", username)
	http.ListenAndServe("localhost:5000", r)
}

This does the same thing as the previous two endpoints and you run it with:

go run myapp.go

Thanks for reading this. What other ways of mocking an endpoint did you find?