how to simulate a user's crontab?

[John Almberg]

I often run into permission problems with user crontabs. That is, a  
crontab run under a user's permissions.

First of all, it seems to me that a user's crontab doesn't have  
exactly the same permission as the user himself. Is this true?

If so, what permissions does a user's crontab have?

Is there anyway I can simulate these permissions on the command line,  
so I can test things before putting them in a crontab?

What I'd like to avoid is the frustrating cycle of putting a line in  
a user's crontab (a few minutes ahead), waiting for it to fire off,  
have it fail, check error logs, try again...

It would be much simpler if I could simulate the crontab's  
environment, and just run the thing from the command line.

Any hope? I'm running FreeBSD 6.3

-- John