CD signal into a phono stage?

I'm trying to sell an integrated amp. Although I have no real reason to believe that there is a problem with the phono stage (since I've never used it), I think it might be a good idea to check it to make sure. How can I do this? Is it OK to run my CD player through the phono stage? Would the signal be too strong and fry the circuit? How about a tuner? There are actually two phono stages - it's switchable between MM and MC. Can I check both stages with a CD player or tuner? If not, any other ideas?

Thanks
Don