Some spells work and others do not. It would be up to the individual to browse through and weed them out. What kind of evidence were you looking for? Visual evidence doesn't always occur. Spells may work but one cannot actually see anything to prove it.
No spells that alter your DNA, such as turning you into a werewolf, vampire, mermaid, growing wings, ect will work. Likewise, flying spells and teleportation spells will not work. Also, usually spells you write yourself work better than someone else's spell, since it's customized by you. Above all, unless you put focus and energy into the spell, it won't work.