You might think that performing load testing is very simple: you create a script and run it against the application. This is however not always the case, as the software under test might generate unique values for each transactions with the web clients. In their two parts articles, Vadim and Max Kleyzit explain how to detect and correct correlations the errors in your load testing scripts.
The article start by defining the principle of correlation that allows web server to manage communication and security with multiple clients. They explain how correlation impacts the virtual user approach used in load testing and how they could cause errors that are difficult to detect when you replay existing scripts. They also propose of typology of load testing errors to explain how you can separate correlations errors from the others.
Load Test Error Classification. Source: http://www.methodsandtools.com/archive/loadtesterrors1.php
The second part of the article provides an approach to fix correlations issues during load testing. The Comprehensive Correlation Method is based on the Test Analyze Fix and Test (TAFT) strategy. This is an iterative process that incrementally improves a solution or a product. This approach is described in a step by step process.
According to Vadim and Max Kleyzit “If you are stuck with a test that cannot pass a run with a single virtual user, this approach will help you to find hidden dynamic values, create missing extractors and parameters and prepare your test script for error-free runs. By mastering this method, you will gain the confidence to correlate any test case that comes your way.”
Read the complete articles
* Eradicating Load Testing Errors – Part 1: Correlation Errors
* Eradicating Load Testing Errors – Part 2: Mastering Correlation