There are many extensions available for Firefox. I personally likes a few of them. I am using them during development and testing. Here is the 5 extensions that I use more often.
- HttpFox – A HTTP analyzer. Very useful to trace the HTTP request and response and to find out the amount of time to complete each HTTP requests.
- YSlow -analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages. This extension dependent on Firebug and the interface is integrated into Firebug. Useful during testing to find out bottleneck and potential area to improve.
- SeleniumIDE -an integrated development environment for Selenium tests. It is implemented as a Firefox extension, and allows you to record, edit, and debug tests. Selenium IDE includes the entire Selenium Core, allowing you to easily and quickly record and play back tests in the actual environment that they will run. This is another useful tools to perform regression test.
- iMacros – extension that allow you to record and replay repetitious work. There many ways to utilize this extension e.g. data entries, testing, pre-sales demo, etc.
I believe different developers prefer different tools and some tools may have more features than the others. Do share what extension you like from the comments box.