Scalability Testing is a non-functional software testing methodology where applications and infrastructures are examined for performance under increased or decreased workload. By determining the server-side robustness and client-side degradation, the organization can then take the required measures to create the best user experience while optimizing infrastructure costs.
What Is Scalability Testing?
A scalability test is a type of load testing that measures the application’s ability to scale up or down as a reaction to an increase in the number of users. In other words, it tests how the system is going to perform during a sudden spike or fall of user request loads. A robust system should be able to adjust to these changes and deploy its resources to ensure a great user experience.
When carried out on software, hardware, and database, Scalability Testing demonstrates the system’s ability to adapt to changes. The app can have an unexpected escalation in the number of users, CPU or memory usage that needs to be addressed. Testing scalability ensures that the system is responsive to the changing requirements and maintains smooth performance for users while optimizing development and operational costs.
Using various parameters like network or CPU usage correlated with the number of users or transactions per second, scalability testing is executed to pinpoint the exact reasons for a system’s failure to scale up or down. Scalability testing is carried out for as long as the system is capable of expanding, in other words, until it fails. Using this information, you can figure out the system’s weaknesses and vulnerabilities.
Scalability Testing vs Capacity Testing
Scalability Testing is not to be confused with Capacity Testing: Capacity Testing is more about measuring the maximum amount of users that an application or infrastructure can handle at a given time while adhering to defined SLAs. While Scalability Testing is more about the scaling up and down aspect, where sudden traffic fluctuations come into play and how the system copes with it.
Capacity Testing measures the number of simultaneous users or transactions per second the app can handle with a good response time (i.e. understand your real user limit), while Scalability Testing measures how well it handles increasing numbers of users or transactions. Therefore, with Scalability Testing, there is a focus on measuring CPU usage, memory usage, network usage, and database usage; not just metrics like number of concurrent users or number of transactions per second. Another key difference is that in scalability testing we measure how the system scales up and down, and not just up like in Capacity Testing. It’s a bidirectional concept.
Related: All You Need to Know About Capacity Testing
The Five Steps of Scalability Testing
In a nutshell, the process of scalability testing consists of five main steps:
- Estimate the potential of the system, both current and future
- Draft test scenarios/cases to force the system to meet new requirements
- Execute the aforementioned tests, if possible with regular intervals
- Record and document the results to detect inconsistencies
- Pass on the data and actionable insights to the relevant stakeholders
You should ideally have a comprehensive Test Script, that accurately mimics the users’ actions and behaviour. The Run-Time Data used to interact with the applications during the Scalability Testing should also be as accurate as possible for best results. Also, since these are data-driven tests, you need to make sure all varying data has been defined and implemented in the process.
Benefits of Scalability Testing
There are a wide range of benefits of implementing Scalability Tests into your development and software testing process. Here are just three instant results.
Improved User Experience
Testing scalability provides you an opportunity to determine user experience under heavy load (e.g, – the holiday season when there are shopping spikes). When putting your system through the stress of upscaling, you can check its responsiveness and overall performance. Later, you can apply the data gained from testing to improve your application performance metrics (for example, response time) and boost customer experience.
Why is user experience important? 40% of internet users abandon web pages that take longer than three seconds to load. The accessibility and diversity of modern tools, websites, and native and web applications has changed users’ expectations forever. This is why making sure that your customers get the best user experience at any time and from any location is a crucial part of your business.
Lower Infrastructure Cost
Scaling up apps can be expensive. Even with cloud computing, microservices, containers, deployment platforms such as Kubernetes, lambda functions or serverless computing. You need to closely monitor your expenses as you scale up. While testing how well the system shrinks on command (scaling down), you need to make sure that resources are freed and expenses go down accordingly, and that you don’t have issues such as memory leakage, a common case.
Scalability Testing helps optimize apps and infrastructures to make sure you are not overspending or concealing bugs by adding (or reducing) capacity.
Faster time to Resolution with Lower Expenses
Scalability Testing allows the detecting and making of changes already in the testing phase. Why is it important? Fixing bugs becomes more and more expensive as the system grows and expands. Your company will save a lot of money if you prioritize Scalability Testing and automate it. Besides execution of this testing, you should also evaluate the results and fix bugs accordingly.
On average, fixing a software bug in the production phase can cost up to ten times more when compared to fixing it in the testing phase.
Elevated Customer Satisfaction
If you launch an application or website that performs poorly and frequently fails, your company’s reputation will take the hit and your bottom line will be affected almost instantly. Lack of customer satisfaction and brand damage are things that are very hard to recover from today. This is why it is important to conduct Scalability Testing prior to moving to the production phase.
How big are the financial losses your company might face? An eCommerce company that makes $100,000 per day will end up losing up to $2,5 million if their website takes one second more to load. Scalability Testing will help you detect issues with web page loading and other performance issues. By fixing these beforehand, you can make sure your customers and users are happy and satisfied.
Top Scalability Testing Attributes
There are multiple attributes you can use to test your application.
User/Number-Related Performance
This attribute allows you to determine when and how the system slows down and breaks by an increased number of users. After you determine when exactly the system freezes (also, why it does so) and how quickly it stops working altogether, you can apply this knowledge to help it run smoother and perform better. Execute tests for a small and middle number of users as well as put it under the stressful excess of users to collect all the essential data.
Response Time
Being a part of what makes user experience great, response time is a very important criteria to be tested. This test point will help you evaluate how long it takes for user requests to be processed during a heavy overload of your system. Using the information extracted from this test, you can change your resources that are responsible for speed and ensure a better user experience.
Memory Usage
Memory usage refers to the amount of RAM space used for a certain task. When testing this attribute, devs can evaluate the feasibility of memory usage and whether it should be optimized. If testers detect issues with RAM, they should aim for less redundancy, reduction of database hits, and so on. Maybe the memory problems stem from the large number of user requests that overwork your database, in which case you may want to add an extra one.
Throughput
Throughput is a number of requests that can be processed within a certain period of time. The exact description varies depending on the application: throughput for an application means the number of user requests whereas in a database you will be measuring the number of queries. As you increase (or decrease) the system load sharply, the web server response time should stay stable. If it does not, developers should dive in and mitigate the issues causing this.
CPU Usage
CPU is hardware which means that you cannot drastically overload it. Efficiently using your CPU is crucially important to ensure long and sustainable results. It should be able to handle new features and carefully and correctly process requests. If you detect a problem during CPU testing, remove dead code, and optimize it. This way, you will prolong your hardware’s life and also save memory.
Network Usage
Being one of the most complicated pieces of hardware, a network requires a lot of monitoring and optimization. Testing network usage will enhance your chances of a smooth upscaling and downscaling with a good response time, which is crucial today. Network usage can be measured by bytes and packets received per time unit. Your application works best when network usage is at its minimum.
Every congestion you face while executing your test scenarios should be investigated and mitigated in order to ensure the best performance. You need to test your application performance under different network usage conditions such as broadband/narrowband, 3G/4G/5G, different WiFi frequencies, on the move and in static locations, and other kinds of scenarios.
Screen Transition
Screen transition means the ability of the system to transition from a single interface to another one across all possible devices. If during the testing phase you detect that the transition takes longer than it should, your code probably needs to be optimized. The goal is to ensure that the application performs well regardless of the number of users accessing information at the same time.
Choosing the Right Performance and Load Testing Tool for Scalability Testing
The benefits of adding Scalability Testing to your Testing Environment have already been covered in this article, but picking the right solution is equally important to actually enjoy them and improve your product’s quality and performance. To derive these benefits in a timely and cost effective manner, you need a Performance and Load Test Tool that is both robust and flexible enough to accommodate all requirements.
Performing a scalability test is easy in theory, but in reality it requires a solution that provides a centralized monitoring and management hub for all related aspects of the process. It should also be able to be integrated with application performance monitoring tools for server-side metrics and understanding server-side degradation, and integrate with CI/CD tools for automation, similar to how it is done with your other load tests.
It should work seamlessly with Cloud Platforms such as Microsoft Azure and Amazon AWS to easily and cost effectively generate the load. This solution should also be easy-to-use, deployed as an on-premise or as a SaaS model, and should require minimal time, effort, and manpower to operate. Furthermore, you should also be able to gain and share actionable insights with all stakeholders.
Once your solution is truly capable of generating the various traffic and network scenarios, while providing you with enhanced visibility and transparency to monitor all relevant metrics, you can start creating robust applications and websites. Scalability goals are dynamic in nature, and your Performance and Load Testing tool should be fully capable of accommodating these fluctuating needs.
Scalability Testing – For Optimal Versatility
To sum it up, your application and infrastructure needs to be versatile enough to be able to withstand the dynamic requirements of today’s market.
With time to market and code quality becoming increasingly important, you need to implement Scalability Testing to make sure that all kinds of fluctuations, upwards or downwards, are not affecting your performance metrics or leading to site degradation. There are no shortcuts to maximizing customer satisfaction and brand awareness while reducing your infrastructure costs at the same time.
You can meet your business goals only by ensuring smooth scalability. With the right Performance and Load Testing Tool you can perform Scalability Testing regularly by integrating it directly into your CI/CD pipeline. You need to make sure the tools are flexible and robust enough. With strong reporting and analytics implementation, you will reap the rewards in no time.
Related: 5 Signs It’s Time to Re-evaluate Your
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