Load Testing

What is Load Testing?

Load testing is about creating production simulations within an application or system that is as near as possible to being a finished product ready to deploy and subject to the masses. By utilizing specialized testing software, load testing allows dev teams to answer questions like “Is my system doing what I expect under these conditions?” and “Is its performance good enough?” As the Microsoft guide Performance Testing Guidance for Web Applications states:

A load test enables you to measure response times, throughput rates, and resource-utilization levels, and to identify your application’s breaking point, assuming that the breaking point occurs below the peak load condition.

Here, “below the peak load condition” simply suggests, again, a testing methodology that falls within the parameters of a load test as opposed to a stress test (which, by definition, is testing a system at and beyond peak load). Load testing can identify system lag, pageload issues, and anything else that might go awry when multiple users access an application or bombard a system with sudden traffic—things that can be easily overlooked in a development and testing environment where code is often checked with individual users in mind. Mix in a hundred or a thousand people trying to access the software or issue commands more or less simultaneously, however, and problems that might not have been detected in solo use cases can suddenly come to light in all their buggy glory.

Why is Load Testing Important?

Load Testing ensures that your application can perform as expected in production. Just because your application will pass a functional test, this does not mean that it can perform the same under a load. Load testing identifies where and when your application breaks, so you can fix the issue before shipping to production. 

Businesses and consumers rely heavily on digital applications for critical functions, so it's important to validate that it can withstand realistic load scenairos. With a higher adoption of digital applications comes higher expectations of quality, and if your application fails in production, it can become costly. According to Gartner, The average cost of network downtime is around $5,600 per minute. That is around $300,000 per hour on average. Avoiding downtime in production is essential, and load testing helps ensure that your application is ready for production. 

The ultimate purpose of load testing tools—and performance testing tools in general—are always to mitigate risk, be it risk to your software’s successful functionality, risk to your end-users’ sanity, or risk to your company’s bottom line. Naturally, all three of these are intimately intertwined, so it’s important to know how they relate to each other and where you, as a developer or tester, can intervene for the greater good. Let us dare to suggest that if you focus on mitigating the middle criterion, user sanity, the other two factors will usually fall into place, and that many load-testing issues actually boil down, in the end, more to users’ perception than to specific ideal pageload times and other technical stats.

How to Start Load Testing 

Getting started with load testing isn't as hard as it has been historically. In the past, learning to load test - creating a realistic scenario, scripting a test, replaying a test, and analyzing test results - required an immense amount of skill and time. Plus, every load testing tool is different. So learning how to use each tool to get the test runs to function how you intend it to is always a challenge.  With LoadNinja though, you can skip this whole process without sacrificing quality or test coverage. 

1. Gather Requirements - what's the most critical functionalities that you need to test? What shapes your end user experience?
2. Map Out Relevant User Journeys - identify how your users interact with your application. This is a great opportunity to leverage monitoring data from any APM tools you may use. 
3. Establish a Baseline - run tests to establish a solid baseline for your application to test against. Any time performance deviates from this benchmark you'll know a deeper dive into test data is necessary. 
4. Automate & Integrate - prioritize load testing as a part of your CI/CD processes & integrate with the tools you already use. 

These steps will provide a good foundation to begin load testing your application.

Load Testing Best Practices

1. Create Realistic Scenarios

   Think like a user would. What is important to your user base? What functions of your application are critical for them? Do they use different devices? By creating realistic load tests, you're able to more closely understand how your application behaves or would behave in production with real users. Real users to a certain extent are unpredictable, so keep randomness and variablilty in mind when evaulating the steps to take in your tests. Mix up the device and browser type so you can feel confident that your application is ready for deployment.  

2. Test Early, Test Often

   Whether your team is adopting an agile, devops, or shift left mentality, it's essential to test early and test often. Frequently performance testing is siloed and starts when a development project is over. However, in the last few years increasing the amount of feedback throughout your software development lifecycle has proved immensely valuable in finding and fixing issues rapidly. Prioritize making performance testing, and load testing in particular, a part of your agile, continuous integration, and automation practices. 

3. Set Realistic Benchmarks

   Optimizing performance requires a deep understanding your application and it's users.  Identify practical & realistic tests that can reflect reality, whether that means selecting devices, browsers, number of users, etc. Plus, load tests can't start from zero. In the real world, it's unlikely that the systems you're looking to update will not be running under load already. So rather than starting from zero and incrementally adding virtual users slowly until you reach the desired load, try running tests after your systems are already under load. This way you avoid the 'false-positives' that can come from starting your load tests from zero.

4. Leverage Real Life Data

   To achieve realistic benchmarks and scenarios, leverage data you already have. Reusing data from your monitoring tools can help illuminate what 'realistic' means in your specific case. In most cases, monitoring tools are running from a proactive and reactive point of view - meaning you can use synthetic and real user data to map out scenarios that failed in production with a synthetic monitor and/or add interactions that your users are already taking with your application into your test scenarios. This can include user driven data, like browsers, devices, user paths, dropoff points, and system based data, like DOM load, time to first byte, and more. 

5. Analyze Test Data to Unearth Underlying Problems

   After running your load tests, the first obvious step is to identify any problem areas & take the next best steps to improving performance for that component. This means correlating performance bottlenecks with code to isolate the root-cause of the problem. Oftentimes this can be difficult if you're using a traditional testing tool because it requires 'translating' the test results into metrics you can leverage to share with your development team (or to use yourself) to dig deeper into the core code instigating the issue. If you're using LoadNinja, this step is no problem, since you're load tests results are browser-based metrics, which you can inspect & debug in real time. 

Selecting a Load Testing Tool

Finding a tool that can support your team is essential. We know that performance testing practices can take a bit of time in the release cycle, but often they are the indicators for success in production.  With performance testing, you can understand how your application is going to perform in production before you deploy, so you can find and fix issues before going live. Testing reveals if your website performs differently under load, whether your code change has unexpected changes, and saves money in the long run by identifying issues before they become costly problems in production. When evaulating a load testing tool, be sure to keep the following factors in mind:

1. Ease of Use - is it easy to create complex, realistic load tests?
2. Accuracy - does it run in real browsers?
3. Scalability - can you increase or decrease usage/use cases, users, instances?
4. Integrations - can you integrate with the tools you use everyday?

Understanding what tool will fit best into your workflows is essential. Luckily, LoadNinja helps teams load test faster without sacrificing accuracy, so teams can continuously release quality software. 

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