If I try this process using a private key of a Casascius token that has already been redeemed / spent, I should see the transaction attempt to occur in the wallet but not get confirmed (obviously because its already been redeemed). I think that will be my final "test" before going at redeeming my tokens.
I think you should be able to tell it from the balances though, no need to create a test transaction to see whether your coins are still there or not (unless I misunderstood you). Just like how you can see the balances from a wallet you imported with a private key/seed phrase.