I've written a patch for Ubiquity and I'd like to test it before I submit it, but I'm not sure how to go about this given the nature of Ubiquity (only used during installation). Is there a way I can build and run it on my own system, or would I have to pull the entire Ubuntu source code and integrate my patch into that, then run a test installation?
There are a couple ways to do this.
You could also use a virtual machine to test, but that has always been more work than it's worth for me. I usually just use method #1.
Those are the easiest ways. You could also grab the Ubuntu source, edit it, build a new package, install it, and then play with it. But you indicated you wanted to avoid that.