(plan 3)

(let ((a 2))
  (let ((a 10))
    (expect "Inner variable shadows outer" (= a 10)))
  (expect "Outer is not overriden" (= a 2)))

(let ((pings 0))
  (defun ping ()
      (set pings (+ pings 1)))

  (ping) (ping) (ping)

  (expect "setting variables in outside context works" (= pings 3)))