How to test nix after building it

After building nix with nix-build, how can I install & use it in my machine, without starting a nix-shell? I guess this is a matter of replacing the symlinks in ~/.nix-profile ?

Say, nix-env -i ./result

But it really depends on the use case. For example on a NixOS I probably wouldn’t complicated things by putting nix into ~/.nix-profile