What happens during a Load Test?

eCommerce managers are increasingly seeing that website Load Testing is something they should bring under their control, to ensure business-actionable results – realizing that simplistic testing in the past has not delivered the brand protection certainty now needed: after all users are a lot more fickle these days, and even the smallest of problems may rattle their confidence.

For those new to the latest, sophisticated Dynamic User Journey approaches to load testing, this document sets the scene.

The example below is based on a typical Load Test project.

Read more on:  Unique Website Performance Testing Solutions

Set Up

A world famous retail brand with an enviable high street pedigree now sees its online business serving hundreds of thousands of  visitors per hour at peak times. Wanting to ensure that the customer service they have become famous for offline, is carried through to their online presence, the company needs to be absolutely certain that their website can handle very heavy traffic and deliver a perfect customer experience to every single visitor on every single visit.


As the site became increasingly popular the eCommerce platform was starting to struggle in busy periods, especially during the big sales or as a result of successful campaigns and promotions.

With the site becoming increasingly complex and relying on the integration of many different systems, the identification of any bottlenecks require in depth analysis and the correlation of many different sources of data. The flexibility of workflow offered users online has also lead to increased sophistication in user behaviour as there are many more ways for customers to interact. This can also make testing more challenging where an organisation is determined to ensure that all these different types of users and usage patterns have been understood and optimised.

It was becoming increasingly clear to the team, that as eCommerce continues to rise in strategic importance the data available from simpler, traditional, load testing was no longer able to provide the level of insight needed. (previous load testing had been done with a third party with tools that concentrates on basic metrics such as concurrent user sessions, page views, or technology driven performance measures ).


SciVisum’s innovative approach to “realistic testing” through the use of Dynamic User Journeys that really “Do What The Customer Does” can provide just the in-depth information needed by all the teams involved at all stages of the eCommerce strategy and execution.

SciVisum work closely with clients to generate as close to a real-life scenario as possible. We do this through building a representative set of user journeys by collating information from  web analytics stats during the peaks hours of the last traffic.

In addition to defining the Dynamic Journeys:  for an effective load test it is important to cover not only a mixture of different journeys, but to weight the traffic generated by each type of journey – in proportion to actual traffic breakdowns from the past.

To accomplish SciVisum’s lead load test Engineer will liaise closely with the client to analyse both the data collected by SciVisum’s load engine and various results from different relevant  areas of the rest of the infrastructure. Working with multiple data sources and correlating the information across all of them enables the SciVisum engineer to identify likely problem areas. In turn this means that tests can be devised to specifically explore those potential problem areas as a complement to the known mix of user journeys under investigation.

Working together in this way means that the client’s staff can focus in on designing and implementing changes resulting from initial findings before re-running the test to see the results.

The tests themselves can involve complex user journeys of many separate dynamic steps and top level measures including:

  • The number of users that can complete a given journey per minute within the expected mix of total journeys.
  • Realistic number of user journeys per hour based on projections from web analytics about how users might “bunch” during different periods.
  • Max pages per hour with further detailed breakdown to reflect the fact that not all pages are equal in the load they cause a system, or how they are called on as a proportion of page visits for a given time period and type of traffic peak.

Another difference with the SciVisum test engine is that it does not simply ‘replay’ a fixed sequence of URLs for each Journey, but dynamically looks into each page to determine the link for the next. Coupled with the ability to understand user behaviour based on web analytics data this enabled SciVisum engineers to ensure that the virtual users of the load test were able to behave, and interact with content, in the same way as real users and so emulate stress conditions accurately when testing for stability.

The Process

The most successful projects involve many different stakeholders at different stages in the process. When this happens it usually indicates that eCommerce is held in high importance throughout the organisation and there is interest in the load test results both from practical, hands-on, users of the data and from participants in the strategic discussions arising from the activity.

The exact process varies from client as each load test is bespoke, but most follow a similar outline.

Firstly an approach is agreed where various stakeholders would take on different project roles/responsibilities at the client and at SciVisum. Often the Web Analytics Manager from the business team will spend time with the SciVisum engineer either, by phone or on-site, to work out user journeys and a sensible mix of those to generate the load based on current traffic or projections for the future. In order to benchmark performance SciVisum also often maintain 24/7 monitoring of  User Journeys, taking measurements of journey completion time every 5 minutes which allows the engineers to make observations that can be passed back to the client team for explanation and provision of context.

Next comes a series of conference calls and on-site meetings involving SciVisum Load Test engineers, Web Performance Lead and Customer Liaison manager with client teams to prepare and agree pre/post actions for the load test. This is the point we agree what metrics to use, and how they correlate to actual traffic on the site.

SciVisum and client tech team agree how access to internal systems monitoring systems can be given to SciVisum engineer:  to maximise the visibility to the Load Engineer all the data during  test, and thus to provide in the Load Test Report appendix, the best engineering insight on the bottlenecks found and their root cause.

The load test is executed and the client IT team provide the SciVisum engineer with data from various pieces of their infrastructure monitoring tools for correlation against the SciVisum load testing data. The engineer reviews all this data, not only the SciVisum test results, and writes a bespoke report detailing his findings and observations, complete with screen shots and detailed descriptions of all errors thrown, and their specific implications for the client’s on-line goals.

The report, with sections appropriate for technical and business users, is then used as the basis for a workshop with all parties involved to discuss the findings and agree actions that the client IT team can take to try and remove potential bottlenecks. Subsequent load tests are then run and results again reviewed during conference calls to agree if any further action is required.

After The Test

Going forward many clients devise a plan of regular Load Testing to ensure changes they make to the platform during the year don’t significantly reduce the capacity of their sites. This is often coupled with use of the Site Release Management tool that is part of the SciVisum website monitoring suite.


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