How do we differentiate between a saint (wali) and a pretender?

A wali (saint/friend of God) is every pious believer. His sainthood does not require the manifestation of miracles. The path to sainthood is through observing the obligatory acts and supererogatory acts, and adhering to the Qur’an and Sunnah. The insane, the corrupt, and the disobedient are not awliya' (saints). Sainthood does not mean having control over the universe, or knowledge of the unseen, or infallibility, or violating the Sharia, or bestowing it upon others. Furthermore, the belief that a wali can appear in different forms, or be in multiple places at once, or claim to be the seal of saints, or strip knowledge and guidance from those who oppose him—all these are false beliefs that contradict the Sharia.