I agree with Oscar that it would be very helpful to know what kind of switches we are talking about. And we need to know what kind of testing you want to do.

If the testing is just to assure that the switches will boot, that the various interfaces will become active when something is connected, and to verify that they will perform layer 2 forwarding, then connecting them to a small switch should allow you to do that testing.

But if you want to test Etherchannel then we would need to know whether the small switch supports Etherchannel. The original post mentions stacking switches. I think we need to be careful about terminology here. To some people putting one switch physically on top of another and providing an Ethernet connection is stacking. If that is what you mean then you should be able to test this well enough. But to some people stacking means to create a stack group, so that all switches can be managed as a single entity, and to provide some enhanced forwarding capabilities. I do not think that you can test this through an Ethernet connection between switches.

So please explain more about what switches you have and about what you really want to test, and then perhaps we can have better answers.

HTH

Rick