Depending on the size of your organization, you may be working in a world with anywhere from one (production) to many (staging, PPE, Dev) different environments, but often none of those are an accurate real-world test environment. For a personal or small-company site, you may only have a production environment, and any change you want to make is being made in production. Many huge companies/teams have complex roll out plans and staging environments but are often missing a true test environment that is a real match for production. Microsoft Docs, for example, has multiple production instances, so we can do safe rolling deployments and we have staging and PPE (pre-production environments, often used for testing new code before it is even ready to be staged). We don’t have a live production environment that matches production closely enough to be used for performance testing though, behind the same CDN, running on the same hardware and without any authentication to corrupt the test results.

Using a secondary environment for performance testing #

There are multiple reasons to run more than one environment including functional testing and safe rollout, but to do performance testing requires a much closer match to production than what I often see.

Let’s say you want to make a change to how your JavaScript is loaded. You can test this in your local dev environment, to make sure it seems to work, nothing is broken. You could do some performance testing, but your local environment is nothing like production in performance terms. Even something as small as domain lookup and SSL negotiation could make a seemingly great perf update have no real-world benefit or to do harm. So, you push your changes to the PPE or Dev environment, where it is up on a server that is hopefully close to production. PPE is only available behind your corporate authentication and doesn’t have a CDN in front of it though, so it isn’t really going to show you what will happen in production either. For functional testing, this is probably good, although you could still miss issues that will only happen in the actual configuration of the live site. For performance testing, PPE isn’t much better than testing on your local box.

A/B testing is often used to get some real-world data on a performance change, which is accurate and useful, if the testing framework itself doesn’t create a change in the experience. A client-side experimentation framework, that modifies something about the page after load, is not a valid comparison. An A/B test is still in production as well, so you are assuming that there isn’t any major negative impact to your test.

What you want is to create a complete copy of your environment including the CDN configuration, SSL certificates, DNS entries and more. If you pushed the live build to this environment, it should produce the exact same test results as your production site. You might need to send a bit of fake traffic to it, to get content cached by the CDN as it would be in production, but otherwise this is your test bed to try out any performance work. You are also going to want a rapid deployment cycle, because you will be making many tiny changes, testing, and then changing them again.

Creating a test site for my personal blog #

I like to play with performance tuning, and I use my personal site as a place to experiment with a ton of minor changes. Up until this weekend though, I had just been pushing my updates to production, because:

  • The impact of a mistake was low (I don’t get that much traffic), and
  • I’m arrogant enough to think my local tests would catch anything major before I deployed.

Neither of these are valid reasons. A personal site is part of your personal brand, a showcase for your skills. If you were a professional editor, and your personal site had some typos, is that giving visitors the right impression? As for my lack of traffic, you never know when someone is going to be looking, and if you only get a small number of visitors, why risk giving one of them a bad experience? Finally, as I suspect most developers know, anyone can miss something and deploy a breaking change that they thought was completely safe.

With all of that in mind, I decided that I needed a proper test version of my site. My blog is a static site, generated using Hugo, hosted in Azure blob storage behind an Azure CDN profile, so to create a copy I needed to create a set of new resources in Azure and Azure DevOps, including:

  • a blob storage account, setup to host a static web site
  • a CDN endpoint, with the blob storage account as the origin
  • a custom domain ( on that CDN endpoint
  • an SSL certificate for that custom domain (automatically created and managed by just flipping a switch on the CDN endpoint)
  • a CI pipeline that is triggered by a different branch in my blog repo and pushes the built site to the new blob storage account

Including a few delays, and looking up various things on Docs, this was up and running in about an hour. Everything I did could have been scripted/templated though, which would have had two benefits: I could spin up another environment with nearly no work at all, and it would be easier to keep the two instances exactly in sync. I didn’t do it though, because I don’t have any plans to need more of these environments and because I didn’t think of it until about halfway through the steps.

There is one slight difference between the two sites though, I added a bit of conditional logic to the robots.txt template in my blog theme to add a site-wide Disallow line if the site was generated for anything other than This change makes robots.txt on stage look like this:

User-agent: \*

Disallow: /

The Disallow statement instructs search engines not to crawl the site, which should keep it from polluting my search engine results and competing with the production site. I could go farther and add a noindex flag to every page, but I wanted to keep the changes between the sites to the absolute minimum.

One day later and having this site has been amazingly freeing. Being able to iterate through random thoughts and experiments with no fear of breaking the live site, led to about ten deployments in a couple of hours. I was able to try:

  • putting critical CSS inline on the homepage (a success!),
  • moving my tiny bit of JavaScript inline (slower!),
  • switching to only system fonts (minor benefit, but I didn’t like the look of it), and
  • then finally rewriting my template to get rid of the need for JavaScript altogether (a 25% improvement in time to Visually Complete).

A different approach using CloudFlare Workers #

Matt Hobbs wrote up this great guide to an alternate way to do some quick performance testing on your site, without creating a secondary environment, and I love it. For my blog, a secondary environment was quick and easy to setup, but doing the same for Microsoft Docs (or for a site you don’t own) would be much harder. Following this path, you use workers to manipulate the responses coming from the live production site. You write scripts to apply your changes, and then test the result.

You should definitely check it out, and I may end up using it for Docs, but it is worth noting that the final result is not a true copy of your environment. In my case, I’m using the Azure CDN for example, but this setup would be going through Cloudflare. As a way to test a variety of changes without a lot of infrastructure though, this is a great option.

Do you really need a test environment? #

There is a hierarchy of needs in terms of what is necessary for your web project. I believe a full-blown production copy site for testing is useful, but for a production site I would put it lower in priority than a safe deployment process.

Outside of work, I’ve often seen WordPress sites that had no way to test any change they made, including upgrading the entire version of their software. At the time, I don’t think I was as disturbed by this as I am now, but it is a terrible situation to be in. There are two different angles to this: reliability and workflow. If you need to update your homepage, is there anyway to get it running where you can show people and review it? If you need to update a critical plug-in or the version of WordPress, can you do it in a staging site, confirm it works 100% and then swap that with the production site… all with the ability to roll back if something is broken? If you can’t do either of these things, you should fix that before you worry about a mirror site for testing performance updates but keep it on your roadmap!