Once addon signing is enforced, all test extensions will either need to be signed, or to be installed at runtime using a mechanism which will only work with restartless addons - see bug 1209338. I don't think it is realistic to sign all the talos addons (pageloader, tresize, damp, tps, cart), so we need to make these unsigned and figure out how to install them.

I had a restartless version of tart/cart, I'll dig it up. But I think the main issue might be pageloader since it's probably the least trivial of the bunch.