(examples-for ⋂
  ("returns a single arg"
   (⋂ '(a b c))
   (a b c))

  ("returns a single nil arg"
   (⋂ nil)
   nil)

  ("returns intersection of two args"
   (⋂ '(a b c) '(a b d))
   (a b))

  ("returns intersection of list and nil"
   (⋂ '(a b c) nil)
   nil)

  ("returns intersection of nil and list"
   (⋂ nil '(a b c))
   nil)

  ("returns intersection of three args"
   (⋂ '(a b c d e) '(a b c d f) '(z b c d g))
   (b c d))

  ("returns intersection of list, nil, and another list"
   (⋂ '(a b c d e) nil '(z b c d g))
   nil)

  ("returns intersection of four args"
   (⋂ '(a b c d e) '(a b c d f) '(z b d c g) '(z y g c d))
   (c d)))