I don't know how you know for sure, but a lot of times you can spot a bad bulb. It'll be squishy and soft or, on the other extreme, it'll be sort of dried out and hollow feeling. My bulbs that have made it seem kind of heavy and firm. When I'm in doubt I just plant them and see what happens!

Turquoise nailed it!

& if there's any firm *part* of a squishy or hollow rhizome, cut it apart & plant the firm part.

you should see this seasons growth tips. they should be white and firm.

Next time you are ready to dig up the tubers in the fall, leave about 8-10" of the stalk, which will have some "green" to it in the center, and store the whole plant that way...you can monitor easily during storage, as long as it stays green you know the tuber is still alive. This worked for me.