(describe 'minmax
  ((context 'call-with-empty-list
     (it-should-be-nil (minmax ())))
   (context 'call-with-list-of-one-element
     (it-should-be-equal-to (minmax '(1)) (cons 1 1)))
   (context 'call-with-list-of-odd-number-of-elements
     (it-should-be-equal-to (minmax '(3 5 2 1 4)) (cons 1 5)))
   (context 'call-with-list-of-even-number-of-elements
     (let ((arg '(3 5 2 1 4 6)))
       ((it-should-be-equal-to (minmax arg) (cons 1 6)))))
   (context 'test-with-incorrect-spec
     (it-should-be-equal-to (minmax '(1 2 3)) (cons 1 5)))))

minmax
(call-with-empty-list OK)
(call-with-list-of-one-element OK)
(call-with-list-of-odd-number-of-elements OK)
(call-with-list-of-even-number-of-elements OK)
(test-with-incorrect-spec NG (expected (1 . 5) but got (1 . 3)))