Everything you need to know about scalability testing
August 16, 2023

Everything You Need to Know About Scalability Testing

Performance Testing
Continuous Testing

When developing and growing your testing strategy, one of the key questions a team should be asking themselves is this: How do I scale this? 

Scalability is hugely important for any testing team that is yearning to expand their capabilities, widen their test coverage, and kick their testing up a notch. But it is not as easy as simply getting bigger and bolder with your tests. The availability of time, money, and other resources like team member head count and skill level all play a role in scalability. 

So, how can you ensure smooth scalability without growing pains? 

An important tactic in your journey to scalability is to conduct scalability testing. Scalability testing helps an organization take the steps necessary to establish the best user experience available while also taking into consideration organizational requirements and costs. 

In this blog, we will discuss what scalability testing is, the process of scalability testing and its benefits, and what components should be tested during scalability testing. 

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What Is Scalability Testing?

Scalability testing is a type of load test that measures an app’s ability to scale up or down based on an increase in number of users. It determines how an app is going to perform during sudden spikes or drops in user requests. 

Scalability is all about changes to the system, and scalability testing is your best bet on finding out how your app is going to respond to those changes. When scaling testing to address going from thousands of users to hundreds of thousands (or millions!), that unexpected increase can strain the CPU or memory availability. 

A great way to account for increases or decreases in users is setting parameters — such as a certain number of users changing per second — to correlate and identify exactly where the system failed in its attempt to scale up or down. 

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Scalability Testing: The Basics

You can take your approach to scalability testing in many directions in terms of complexity. But, basically, a start-to-finish scalability test looks like this: 

  1. Identify what you believe to be the potential capability of the system — both currently and in the future. 

  1. Develop test scenarios or use cases that will push the system to meet new requirements. 

  1. Now you execute those tests — at consistent, regular intervals if possible. 

  1. Let the data speak. Record the results top to bottom to identify any inconsistencies. 

  1. Take the data and any insights you may glean from it to the next link in the chain to action. 

  1. Repeat regularly. 

Your test scripts should mimic a user’s behavior as accurately as possible. Ensure your test data is properly defined and placed where it is supposed to be. After all, your tests are only as good as what you put into them. 

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The Benefits of Scalability Testing

Incorporating scalability tests into your testing strategy will go a long way in helping you ramp up the scalability of your testing overall. Doing so, you will experience a few major benefits in your development process. 

Lower Cost

As mentioned, scaling up your testing can be expensive. That is why it is imperative to approach it with your available resources in mind. Scalability testing optimizes your app and your overall testing infrastructure to ensure you are not spending too much or inadvertently hiding bugs when you scale your capacity up or down. 

Find Fixes Faster

Scalability tests help immensely with finding and fixing bugs in your test environment faster. The longer you allow bugs to fester (pun intended) in your testing environment, the more expensive it becomes to address them later down the road.  

Improved UX

Testing your app under a heavy load — like simulating peak traffic events such as Black Friday — lets you know where the holes are in your user experience. It allows you to check for responsivity and app performance. Then you can leverage the information gleaned from scalability tests to improve key metrics like response time for an overall better customer experience. 

Happy Customers

This is the result we are all striving towards after all, is it not? A poor user experience is the fastest way to lose a customer. As the adage goes, it takes a tremendous amount of effort to build trust and very little to lose it. Scalability testing ensures your app can handle whatever is thrown at it — resulting in happy customers and fortified brand reputation. 

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Key Components for Scalability Testing

You can put pretty much any component of your app through scalability testing. But there are a few that you want to consider prioritizing. 

Network Usage

A network requires a lot of love and attention. It is a vastly complicated component of your app. By putting your network usage through scalability testing, you can improve upon and establish smooth downscaling and upscaling. 

Your app will work best when network usage is at its lowest. It is important to test it under a wide range of network usage conditions such as 3G/4G/5G, broadband/narrowband, various WiFi frequencies, when the app (the device) is on the move or in a static location, and more. 

User-Related Performance

This is a big one for testing the performance of your app. When the number of users of your app increases, does your app slow down and break? Does your system freeze? With scalability testing, you can find out how quickly your app slows down or stops working entirely, thus applying that information in order to ensure a smooth performance. Create tests that run against a small number of users and a large number of users and any amount in between. 


This metric tells you what your app does in the face of a number of user requests within a specified timeframe. When you scale down or scale up the system load drastically in a period of one minute, the goal is for your server response time to remain stable. If it does not, investigate why that is so and address it. 

Response Time

Response time is the metric that affects users the most. Every component leading up to how a user interacts with your app could be perfect, but if — for whatever reason — a user is waiting for upwards of a minute or two, that spells doom for your app. Scalability testing against response time will determine how long it takes for user requests to be processed during a period of heavy load on your system. Use what you learn here to optimize system speed. 

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Bottom Line

For your app to grow and thrive, you need to strongly consider its capability for scaling. It is imperative if you want to improve the quality and performance of your app.  

Scaling your app can be complex, but it does not have to be if you partner with the right testing platform. BlazeMeter offers unrivaled scalability of up to two million users(!), which allows teams to get the absolute most out of their app. By leveraging the industry’s most-trusted performance tester for your scalability testing, your app will truly be capable of handling whatever it is put through. 

What are you waiting for? You can start testing with BlazeMeter for FREE today! 

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