This is true. Just be sure & call first to let them know you are just testing & sending signals. Otherwise, you will have emergency vehicles at your home.
Also, if you don't disconnect your siren(s) in the panel, you will have to deal with the noise while testing.
Sometimes it is better to have the alarm company do it if you are unfamiliar.
About the "major power loss", make sure your alarm system is still powered by the back up battery inside the panel while the AC electricity power is off. The keypad should still be functioning like normal. This will let you know that your back up battery is still working.
Make sure your system is well grounded to earth ground & has a surge protector on the main transformer.