Fiddler is a Web Debugging Proxy tool which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect traffic and can be used by developers to debug web programs. When doing web application testing, it can also help testers inspect and examine the traffic between the user side of a web application and a web server. Below I’ll talk about the tool from a tester perspective, and discuss some of the simple uses that we’ve come across.

1. Session Inspection

For instance, when you are testing an online payment system a lot of the information is sensitive.  With Fiddler session records, you can find out how the request and the provided user data go or get redirected. Also you can tell whether the sensitive data, such as passwords, and card numbers, are encrypted, as required, before they are send to the internet.

As QA, we are often asked to test some features that are not fully developed as managers expect testers to get involved as early as possible. To get started, you can begin by looking into session information under Inspectors / WebForms to examine underlying data that are not yet ready to be displayed in the UI.

2. Performance Inspection

This is a feature of Fiddler that can be used when examining HTTP (S) sessions. Using Fiddler, you can see each element that is communicated between the client end and the server end under the ”Statistics” tab, including how many requests were sent to the server, bytes sent and received, time sent and received, etc. This is useful for instance when managers have a request to measure the performance of the home page. To complete the task, you can start with Fiddler to track the performance statistics and get a general state of its performance. But this is definitely not a replacement for LoadRunner which can be used to test web applications through supporting protocols with complex business workflow, transactions and load generating strategy.