That is why modern spellmakers have the tlateochihualapaztli, or the Metaspell, in which other spells can be cast and isolated from the outside world, and their effects recorded and carefully combed through for problems; testing of more advanced spells may also need the iztlacatlamatini, or the Fakespell, which can emulate the weave of other spells without actually casting them, letting other spells talk to it without knowledge of its illegitimacy.