Redirecting HTTP Requests in a Test to a Particular IP Address – Sauce Labs

Editing the Host file of the virtual machine will not work if Sauce Connect Proxy is in use. If you are using Sauce Connect Proxy, the Host file of the machine running Sauce Connect Proxy will be referenced and you can make the desired changes there.

Tests often include http requests to various domains/endpoints. DNS will, of course, resolve those domain names to an IP address.

Sometimes tests need to redirect their normal requests to a development server. These domains will not be found by DNS. A solution to this problem is to add an entry to the local hosts file of the computer running the test, thus making the domain resolve to the IP address of the development server. For example, one might want www.fonts.com to resolve to the IP address 196.118.45.9, because that is the IP address of a server that holds a development version of the fonts.

This can be done on a Sauce Labs VM with the help of a pre-run executable.

To make this happen, follow these steps:

Write a host file script with the URL redirect to the new IP address.
Upload the script to a publicly accessible location, like GitHub or Sauce Storage
Set prerun capability in your test script to load the script as the host file in the Sauce Labs virtual machine.

Below are examples of steps (1) and (3).

The Host File Script

Here are examples of the host file script, EditDNS,in both OS X/Linux and Windows versions.

#!/bin/bash
echo "196.118.45.9 www.fonts.com" >> /etc/hosts

@echo off
echo 196.118.45.9 www.fonts.com > %temp%\temphosts.txt
type C:\WINDOWS\system32\drivers\etc\hosts >> %temp%\temphosts.txt
copy /Y %temp%\temphosts.txt C:\WINDOWS\system32\drivers\etc\hosts

Setting the prerun Capability in Your Test Script

Having created and uploaded your host file script, you now need to refer to it using the prerun capability in your test script, as shown in this Python example.

#!/usr/bin/python
# -*- coding: UTF-8 -*-

import unittest
import time
from selenium import webdriver

class Selenium2OnSauce(unittest.TestCase):

    def setUp(self):
        self.desired_capabilities = webdriver.DesiredCapabilities.CHROME
        self.desired_capabilities['version'] = '56'
        self.desired_capabilities['platform'] = 'OS X 10.11'
        self.desired_capabilities['name'] = 'Editing the DNS'
        self.desired_capabilities['prerun'] = {'executable':'[LINK_TO_SCRIPT]', 'background': False }
        
        self.driver = webdriver.Remote(command_executor = 'http://SAUCE_USERNAME:SAUCE_ACCESS_KEY@ondemand.us-west-1.saucelabs.com:443/wd/hub', desired_capabilities = self.desired_capabilities)
        self.driver.implicitly_wait(30)    

    def test_sauce(self):
        self.driver.get('http://www.fonts.com')
        title = self.driver.title
        self.assertEquals("Cross Browser Testing, Selenium Testing, and Mobile Testing | Sauce Labs", title)  

    def tearDown(self):
            self.driver.quit()

if __name__ == '__main__':
    unittest.main()