To be able to test it, one needs a socket that fits the CPU. That socket is attached to a board, and the board exchanges data with the testing equipment. Much easier to get a mobo that fits the CPU.
Or, you could accept returns for it, in case it does not work.
Did you use the CPU before? Is it a newer style Intel without pins like LGA775 or later? If the answer is yes to both of those questions and you handled the CPU properly, did not touch the contacts directly, and kept it put away in a sealed plastic bag or container... then the CPU should be fine. When selling it, just offer a 3 day return period or something.
If you didn't use the CPU recently, and it is the older style Intel or AMD with protruding contact pins (and no metal cover over the silicon)... then you should be extra careful in handling and inspecting the contact pins (and the silicon if it doesn't have the metal cover). In the case it is AMD or older Intel you really should try to borrow a board or computer to test it. It is easy to bend a contact (or chip the silicon), and also if it has been a long time since you used it, there is a possibility of corrosion on the contacts if it has been handled or stored improperly.
No matter what, I will have to agree with house70 on the return policy if there is no way you can test it. But don't give them longer than 3 days.