Setting up a Firefox testing environment

In light of jumping into open source development, I first decided to explore Firefox and to try and learn a bit about it, its architecture and how to accommodate a testing environment for it.

First thing was first: downloading a prerelease version of Firefox. I had two choices: download the current (but less stable) nightly build or the more stable but less current beta. I chose to test a nightly build, but could have chosen both and simply installed to different directories. Installation was simple and straight-forward and just like release versions of Firefox. One thing of note was that pre-release versions were installed in a separate location from release versions, under the name Minefield. Genius, this way I could have both installed concurrently!

From here, I came into an issue:my release version of Firefox had been heavily customized by me, but what if I wanted to test the default configuration? After some research I changed the properties of the shortcut for Minefield to add the command-line argument -P (apparently identical to the -ProfileManager argument), which opened up a profile manager for me to create a secondary profile. Firefox allows for different profiles (which group configuration, extensions and more) to be used to run Firefox, but there is always a default. Upon making my new profile (named Testing), Firefox opens normally. I then closed Firefox and re-modified the command line in the shortcut to include the new profile name in quotes after the -P like so:

This was all fine and well, except that Firefox is designed so that by default only one instance can be run at once. By that I mean if run my release version, minimize and attempt to open Minefield, another instance of the already-running release version pops up. Through lecture with David Humphrey, I learned that the way to resolve this was simply to add the -no-remote command line option with the -P option (after the profile name) to allow multiple instances to be run under different profiles. With this little tweak, I now have completely independent testing environments setup for concurrently testing various Firefox builds.