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Load Testing Explained: How Load Tests Work? Do You Need It?

What is Load Testing?

Load testing is the process of assessing how something works under varying loads. In the context of websites, it is carried out to give an idea of what website performance will be like under different conditions. Knowing this information can help with performance fine-tuning.

Building a website isn’t all that difficult. Unfortunately, many website owners fail to properly plan for increasing numbers of visitors. Handling one or two requests is fine, but what happens to your site when it gets 50 to 100 requests in short periods of time?

That’s where load testing comes in handy.

How Does Load Testing Actually Work?

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Never wait until visitors are flooding your site and encountering 429 or 508 errors. Live websites should always strive to avoid any possible downtime. Load testing can help you with advance planning to avoid these scenarios.

Most load testing is carried out with software. Since the activities will impact site performance, they are typically carried out before websites go live. This avoids the performance impact and gives you the opportunity to rectify potential issues in advance.

The basic principle is to use scripts to mimic certain scenarios and observe how the website responds. The tool or software used will then load the pre-defined scripts and run them according to other parameters which you can set.

Load Testing Reports – Examples

During the test, data will be recorded at multiple points such as the CPU, memory, Input / Output (I/O) Operations, and more. Some tools may simply provide you with this data, while others are advanced enough to help you analyze the results and even recommend action plans.

Example – Number of Errors Chart generated in Loadview-Testing.com report; it illustrates the number of error sessions by error type.
Example – Average Response Time report generated using Loadview-Testing.com.
Example – RedLine13 offers easy-to-read visual results.

Benefits of Load Testing

With the results provided to you by the load testing tool, you can make adjustments to your site to help it plan for the behavioral scenarios you’ve tested for.

Some of the potential advantages include:

  • Resolving performance bottlenecks – If you note your site slowing down in specific scenarios, it might be due to bottlenecks in specific web hosting resources. For example, some database queries will consume more CPU time.
  • Increased agility – Knowing potential points of failure can help you plan for better resource scalability. This is more helpful if you’re on customizable plans such as VPS. If you note increasing resource consumption, you can provision for it in advance.
  • Better manage ROI – Knowing the cost of resources and their limitations can help you keep costs to more effective levels. Over-provisioning can cost significant amounts of money, and load testing can help you avoid that.

These are just some of the many benefits that effective load testing can bring.

What Tools to Use?

Example – Loadview is one of the more complete solutions available in the market and today is based on a cloud service model. Price starts from $199/mo, free trial available.

Load testing tools you can take a look at include Loadview-Testing by Dotcom Monitor, LoadNinja, SmartMeter.io, and WebLOAD.

Depending on the tool you choose to load test your site with, each may come with different features. The most basic will simply involve simulating an ever-increasing load and halting when your site crashes.

Other tools may be capable of generating a simulated load that mimics different user behavior, such as performing queries, changing pages, or loading other functions. Some may even be able to map out logical flows for each individual scenario.

We’ve included a mixture of advanced and basic (aka. cheap and expensive) load-testing tools, including a couple of open-source options, in another article here. Do check it out if you were looking for a suitable load testing tool.

Examples of Load Testing Scenarios

To get a better idea of load testing, let’s example of some possible scenarios.

1. Load Testing Your Blog

Stress Testing
Example – Load testing report of a WordPress blog hosted at Cloudways (source).

Blogs are normally more straightforward since their main objective is simply to convey information. However, depending on what you actually do with your blog, more activities may be possible. A possible combination of scripts may include:

  • 15 users loading pages at the same time.
  • 15 who decide to log in to their subscriber accounts and then log out.
  • 15 users who load pages containing complex data loaded in tables

2. Load Testing Your eCommerce Site

eCommerce sites must perform load tests or face disaster. They need to be able to manage a series of complex situations easily. For example:

  • 20 Users browsing product catalogs
  • 25 Users adding and removing items from shopping carts
  • 30 Users logging into their accounts to modify profiles

As you can see, the possible combination of scenarios can be hugely daunting. The results are possibly even more comprehensive. Proper planning needs to be carried out in order to get realistic results from load testing activities.

Load Testing vs. Stress Testing

I’ve seen some people use the terms load testing and stress testing interchangeably, but this isn’t correct.

As you can see from what I’ve mentioned so far, load testing actually probes using a combination of complex behaviors.

Stress testing on the other hand is more rudimentary. It is designed to test the overall capacity of your site to handle high volumes of traffic. In almost all situations, stress tests will simply flood a site with requests until performance drops and the site eventually stops responding.

Aside from seeing at what point the site will eventually fail, stress testing also observes how well the site will recover from the failure. Not all sites will recover by themselves – some will simply go offline until you intervene.

It is normal for website owners to carry out both load and stress testing.

Final Thoughts

Like anything else that involves websites, the price of load testing can vary greatly. There are simple tools that you can use that will offer some level of benefit for free. However, for more highly commercialized sites, expect to pay significantly more if your needs are comprehensive.

It’s simply part of the cost of doing business online. Yes, you can avoid paying these fees, but as I’ve noted above, over-provisioning resources can end up costing you even more. What’s worse is that while paying for that continuously, you still don’t know when your site may fail.

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Article by Jerry Low

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