Yes. I'm not standard issue, and always have to make changes to the pattern out of the envelope.
If it's something that I'm pretty sure will work with my usual adjustments, I make a quick practice one without all the finishing and check to see if it goes together properly, fits, looks good, and I still want to make it out of my nice fabric.
The less I know about a pattern and how it's going to fit me, the more seriously I treat the toile/muslin stage from the beginning. I rarely take it super-seriously, but it's totally worth it when I do.
If I've adjusted a pattern that fits me with details from another pattern or vice versa, I might sew up a test garment, or just baste the first version together to ensure it works before stitching with small stitches. It depends on the amount of changes to/from that base fitting pattern.
I've spent lots of time fitting patterns over the past two years. Just recently begun saving well-fitting patterns on card so it will be easy to compare them to new patterns and make adjustments, and really easy to trace off a new one when sewing inspiration strikes. I've always had to plan so far ahead with my sewing in order to end up with stuff that fits and goes together. It will be nice to be more spontaneous once in a while. 'Cause I still love to make plans for sewing more than actually sewing it.