[Samba] How to tell a machine is properly joined to a domain?

[pisymbol .]

I have been using 'net ads testjoin' but the issue is it seems to ask for a
password when the box is not joined to a domain (even if I specify '-U
username%pass'). This *seems* like a bug - I would expect it to pass or
fail using the creds passed in.

Is this by design and if so, why? Is there a better alternative? ('net ads
info'?)

-aps