Load testing tells you how your website, app, or API behaves before traffic exposes a weak point in public. If users complain about a sluggish site, if performance drops when traffic is high, or if a new feature makes the system lag, load testing gives you evidence before the next release.
Load testing is a branch of software performance testing. It subjects a website or application to simulated workloads that stretch its operational capacity so you can assess performance, reliability, and recovery before slow pages affect user experience, search performance, or conversion.
The advantages of load testing
Some benefits that you get from load testing include:
- Prevent downtime with analysis. It helps you run various scenarios mimicking real-world usage to gain different insights on your users’ behavior and website performance. This is an accurate and quantifiable way to discover new methods to add value to your website and improve your business.
- Save money long-term. Although a load test can lead you incur costs it helps you save money in the long run by uncovering emerging problems that you can fix for much less. It also helps maximize your website’s efficiency which saves you from over spending on maintenance.
The goals of load testing
At its core load testing is a means of measuring metrics. It therefore means that there are goals that underlie the quantifying of the specified metrics. Some of the things it seeks to find out are:
- How robust the system is and more so how it recovers from any errors
- How efficiently the resources the system has at its disposal are being used e.g. if you have a fast processor and low RAM it means that the hardware resources are under-performing. In such a case load testing will reveal where relevant improvement should be done to achieve optimal output. This is also applicable in assessing efficiency of a website’s resources
- What hampers the system’s ability to fully handle its work load i.e. bottlenecks
It is important to note that you need to differentiate between goals behind load testing and the means by which you arrive at load testing.
Load testing metrics to analyze
Once you have identified your goals for carrying out load testing, you need to know what metrics to measure. A few key things to look at can include:
Throughput: How much bandwidth a website uses up while conducting the test. It indicates the amount of data sent and received from the servers.
Error rate: How frequently errors occur when a website is processing requests and at what stage they do occur.
Response time: How long a website takes to respond during the highest levels of activity (peak time) and as measured over a period of time (average time).
- Requests per second: How many requests are sent to the server
- Concurrent users: How many virtual users are active at any given time
- CPU utilization: How well the CPU is utilized as the website processes a request
- RAM utilization: How much memory is utilized as the website processes a request
- Number of failed or passed transactions: The overall amount of successful and unsuccessful transactions
- Wait time: How long it takes once a request is sent to when the first byte is received in response
Methods of load testing
most teams now describe load testing with a broader taxonomy. The method you choose depends on the risk you need to prove or rule out.
Baseline load testing
Baseline load testing measures normal expected traffic. It helps you compare one build with another and catch performance regression before it reaches customers.
Stress testing
Stress testing pushes the system beyond the expected workload to find the breaking point. This shows what fails first, how the system recovers, and whether failure is graceful.
Spike testing
Spike testing models sudden traffic increases, such as launches, sales, press mentions, or viral campaigns. It is useful for validating autoscaling, caching, queue behavior, and rate limits.
Longevity testing
Longevity testing, also called soak or endurance testing, runs the system under sustained load for a long period. It can reveal memory leaks, connection leaks, log growth, and resource exhaustion that short tests miss.
Volume testing
Volume testing assesses how a website or application behaves with large amounts of data. It is useful when the risk comes from database size, file volume, imports, search indexes, or reporting workloads.
6 load testing tools
There are a variety of load testing tools you can use to accurately mimic the real load on your site and obtain actionable feedback. The best choice depends on whether your team wants an open-source tool, a code-first workflow, real-browser tests, managed cloud execution, or enterprise governance.
Apache JMeter
Apache JMeter remains one of the most widely used open-source tools for load and performance testing. It is flexible, mature, and useful for teams that need broad protocol support and a large community.
Grafana k6
Grafana k6 is an open-source load and performance testing tool for developers, SREs, and QA teams. Tests are written in JavaScript or TypeScript and can run locally, in CI/CD, or in Grafana Cloud k6.
Gatling
Gatling is a high-performance, code-driven load testing tool. It fits teams that want simulations defined as code and maintained alongside the application.
Locust
Locust is an open-source load testing framework where user behavior is written in Python. It is useful when your scenarios need realistic flows, custom logic, or Python-native test ownership.
LoadView
LoadView is a cloud-based load testing platform from Dotcom-Monitor. It is a strong fit when you need real browsers, geographic load generation, API tests, or managed infrastructure instead of maintaining your own load generators.
OpenText LoadRunner
OpenText LoadRunner is the current enterprise LoadRunner product line. It is best suited to large organizations with complex applications, governance requirements, and dedicated performance engineering teams.
Factors to consider when selecting a tool
The best tool is the one that most suits your needs to deliver the best results for your specific context. Things to weigh include:
- The cost of the license if you opt for a paid tool
- The protocols you will use. You need a tool that supports the relevant protocols involved for it to deliver
- How often the vendor or developer updates it and whether there is any support offered in case you run into technical difficulties and need assistance
- How expensive it will be to train any staff on using it, be it monetarily or time wise
- The software or hardware that is required to run the tool effectively
- Whether your client has a particular preference for any specific testing tool
Also consider how the tool fits into CI/CD, observability, release management, test data safety, and collaboration. A tool that generates load but leaves results hard to compare will not help the team improve with every run.
9 tips for website load testing
The best load test that will deliver valuable and actionable feedback to help improve your website is one that you prepare for. Load testing goes beyond just simulating a desired scenario. Here are a few things to do to make sure you get value for your money when testing:
Schedule your testing
Testing once every two weeks is not the right rule for every team. Schedule load testing around risk: before major releases, migrations, seasonal campaigns, infrastructure changes, and updates to critical user journeys. High-traffic systems may also run lightweight performance gates on every build.
Use real browsers
Aim to use real browsers as much as possible to generate more accurate results as they better mimic real-world users as compared to virtual browsers. If need be you can add virtual browsers to reach your target.
Set accurate benchmarks
Use your own data before copying a competitor benchmark. Realistic baselines come from production traffic, service-level objectives, historical peaks, conversion paths, and the user journeys that matter most to the business.
Create a team
A well-executed load test can deliver high quality insights that significantly impact your website in a meaningful way. Assign specific tasks to a relevant team member and let them know that they are in charge of delivering on it. Coordinate the who-does-what during a test to foster collaboration. The result will be a test that encounters minimal barriers to its smooth operation. Consider a self-service solution if you have a complete team and a full-service tool if you can’t constitute a big enough team.
Critically analyze your data
A well-timed load test is one that is executed when the website is at its busiest. Study your analytics over the last 12 months to pinpoint when traffic is at its highest point. When testing, aim to go around 20 percent higher than your peak traffic volume to ensure that the website can handle its greatest number of users without significant problems.
Record all information
Maintain a record of all the results generated from each test in a system that is easy for all team members to access. It will help narrow down any bottlenecks that crop up to find the root causes without talking too long. Always monitor your overall infrastructure and servers to stay on top of any emergent issues.
Cross reference the results
Ensure that you match up the results of a specific test to its timeline. Cross reference all the resulting timelines and test results to look at the complete picture when analyzing insights. This will give you a well-rounded understanding of any problematic areas than if you individually analyzed the tests for insights in isolation.
Build up with every test
The best way to find out how the website performs at different load levels is to start small and keep increasing with every test. Compare the metrics you are interested in with every increase in the number of users to gain insight.
Free vs. paid tools
Cutting down on operational costs is admirable for a business but not when it affects the quality of services provided. Avoid using the price of a tool as a determinant in whether to adopt a free or paid one.
The goal of a load test is to mimic real-world user conditions as much as possible for best insights. Assess if you can achieve this through a free tool. If not, a paid one may be an option to consider in order to effectively gather the data needed to improve your site’s performance. The more a load test can copy real-world user behavior the better the results for your website.
Make load testing repeatable
A load test is only useful if the next test can be compared to it. Define the critical journeys, workload model, test data, environment, thresholds, monitoring plan, rollback plan, and remediation owner before the test begins.
Then record what happened. A recurring checklist in Process Street can assign owners, enforce pre-test checks, capture evidence, and make every performance run comparable to the last one. Teams that already use structured workflow management software can turn load testing into a controlled operating process instead of a shared document that goes stale.
Get started load testing
Load testing is an important strategy in making your website more user friendly and efficient. The data gathered from testing in different scenarios provides different insights that help point you to improvements that need to be made. There are varied load testing tools to suit various needs and contexts. Planning your load test and understanding what metrics to look for are key in deriving high value results. A test that is well executed carries significant and material impact on your website and business.
This guest post was submitted by Glenn Lee, Marketing Assistant at Dotcom-Monitor