I test as soon as I can! I'd much rather find a goof while it's easy to fix.
A variation of this is for me to install keyless fixtures early in the game, and get power to the lighting circuits. This gives the rockers, painters, etc., some light to work by (as well as prooving my circuit).
Generally, as a rule, I run at least 1 branch circuit consisting of a few receptacles, and a few lights, and run it through "common areas" of a dwelling so people can see and work during the construction period. I also energize the laundry receptacle and a GFCI recpetacle beside the panel. That's it.
Never here either. But I do double and triple check the wiring runs to make sure none have been forgotten. As far as crossed wires in a box goes, those are simple to troubleshoot and can be fixed at the finished stage. Also, I use a digital camcorder to videotape all the rough wiring in a new home just in case...
"Will it be cheaper if I drill the holes for you?"
Mark, I'm a bit paranoid. I simply have little faith in my abilities to keep things straight- especially if my work is interrupted by other jobs, etc, and not done in a single sitting.
Before I hook up a new circuit, I usually check everthing with my meter. I've discovered a few goofs that way. Doing this also lets me verify my circuit ID.
Apart from wiring goofs I might make, there are always those boxes that the rockers have buried, and you've forgotten about.
So- I install devices, test, power up, then go around checking. I do this one circuit at a time, and put a piece of masking tape with the circuit number on the cover plate. (Observant readers will recall seeing some of this marking in pics I've posted). If there's a problem, that point gets a red piece of tape. This way, I can back off and see patterns (if there are any). It also lets me keep track of what's been fixed.
A bit anal? Perhaps. But, you know, it can be prety hard to keep track of what all those switches serve- and I really like being able to say when I leave thet "my stuff works." Call-backs are a losing proposition.
Rarely do we test everything - usually fire up a panel outlet and a bathroom GFI (keep some old ones on the truck and reuse them) so the other trades have power - sometimes pigtail sockets... Once in a while an outside GFI for siding and roofing guys.
Biggest paranoia is missing a feed - always strip a short bit of insulation on all feeds and check to make sure they are all there. Painters made me give up marking feeds with romex sleeves.
Digital camera sometimes - lable home runs with romex sleeves.
Since I'm a one man shop, I rarely get to work a job start to finish, I'm always getting called away for service calls, etc. SInce my memory isn't what it once was (I think), testing is my SOP when using cable wiring methods.
When I do my make-ups, I connect a battery & buzzer at the panel. As I make up the boxes, in order from start to finish of a circuit, I short the hot to the neutral & listen for the buzz. This has the added benefit of annoying all the other trades for a day or two.
Few things are harder to put up with than the annoyance of a good example.