Introduction to Load Testing: Part One
The website is completed or mostly completed and you have been advised to do a load test, but you are not quite sure were to begin. First things first, a basic understanding of load testing procedure is needed. The load testing procedure mostly involves understanding the web-application that will be tested. Understanding the applications refers to many different factors such as:
- Understanding the functionality of the website.
- Understanding the general network layout.
- Understanding the software and hardware used by the system.
These factors are useful for a number of reasons, not only do they make the load testing process easier, but they can help you decide which load testing tool is appropriate for your testing needs.
This post will focus on understanding the functionality of the website. Not everyone might have the time or resources to test every single function of the site, but understanding the functionality of the website will be helpful in figuring out what parts of the site really need to be load tested. Making the test cases as simple as possible is generally good practice. In theory one could download a load testing tool and record a test case of a user hitting every single page, then generate a load test of multiple users doing the same thing. However that is not particularly helpful nor realistic for most websites. Yes there are some website with very few pages in which users will click on every page and in that sense, a test case including all the web-pages is ideal, however:
- Most websites are more complex and not every user will click on every single page on the website.
- On average, most users will only click on a certain number of pages, so understanding your high traffic areas is helpful.
- A good formula to use is to test 20% of the pages that generate 80% of the load to the website.
- Knowing the high load pages and using them to generate test cases is generally good practice.
Understanding the functionality of the website also includes knowing the acceptable performance for the website. There is no set formula for figuring out the performance goals of a website. The performance goals change with each application, therefore it can be challenging figuring out the appropriate values, but doing so is very valuable. Studies have shown that as the performance of a website decreases, the number of users who give up on the site and go somewhere else increases. There are load testing tools like Web Performance Load Tester that:
- Let you edit the performance goals of the website.
- Generate a baseline performance report.
A Baseline Performance Report describes the initial performance of the system when not under load. This is particularly useful because the website is unlikely to be faster then when not under load, therefore if it is already failing in performance goals with only one user, that is something that is very important to know as quickly as possible.
Now that we have more of an idea as to why understanding the functionality of the website makes load testing easier; I will go into more detail about the importance of understanding the general network layout of your web application in Part Two.