I would NEVER check an alternator by disconnecting the battery, you could fry your entire electrical system (rare, but possible). The battery absorbs any AC current the alternator may be putting out due to fried diodes on the rectifier bridge, so if the battery is removed, the entire car may be subject to AC current, and electronics don't like AC current. You could fry the radio, the ETACS, the PCM, all that. Furthermore, removing the battery may even fry those diodes, making an otherwise serviceable alternator bad. Yes if the car cuts off the alternator is bad, but you won't know if it was good before you disconnected the battery. Just because it hasn't happened before doesn't mean it won't happen this time. It's not a good thing to do with today's computerized cars, which is why it's an old method.
Read these links for how the charging system works, how to check an alternator and each one has a warning about disconnecting the battery to test an alternator.
http://www.troubleshooters.com/dont_...ct_battery.htm
http://www.wikihow.com/Check-an-Alternator
http://www.bcae1.com/charging.htm
Hope this helps.