(define (test-merge)
  (and
   (equal? (merge '() '()) '())
   (equal? (merge '() '(1 2 3)) '(1 2 3))
   (equal? (merge '(1 2 3) '()) '(1 2 3))
   (equal? (merge '(1 2 3) '(1 2 3)) '(1 1 2 2 3 3))
   (equal? (merge '(1 2 3) '(4 5 6)) '(1 2 3 4 5 6))
   (equal? (merge '(4 5 6) '(1 2 3)) '(1 2 3 4 5 6))
   (equal? (merge '(1 4 7 11) '(3 4 9 12)) '(1 3 4 4 7 9 11 12))))

(define (test-get-elements)
  (and
   (equal? (get-elements even? '()) '())
   (equal? (get-elements even? '(1 3 5 7)) '())
   (equal? (get-elements even? '(2 4 6 8)) '(2 4 6 8))
   (equal? (get-elements even? '(1 2 3 4 5 6 7 8)) '(2 4 6 8))
   (equal? (get-elements even? '(1 ((4 7 6) 8 (10)) (11 12))) '(((4 6) 8 (10)) (12)))
   (equal? (get-elements odd? '(1 ((4 7 6) 8 (10)) (11 12))) '(1 ((7) () (11))))))

(define (test-remove-last-item)
  (and       
   (equal? (remove-last-item 11 '()) '())
   (equal? (remove-last-item 11 '(11)) '())
   (equal? (remove-last-item 11 '(12)) '(12))
   (equal? (remove-last-item 11 '(11 11 11 11)) '(11 11 11))
   (equal? (remove-last-item 11 '(4 7 8 10 7 11 12)) '(4 7 8 10 7 12))
   (equal? (remove-last-item 11 '(4 11 7 8 10 7 11 12)) '(4 11 7 8 10 7 12))
   (equal? (remove-last-item 11 '(11 4 7 8 10 7 11 12)) '(11 4 7 8 10 7 12))))

(define (test-iterator)
  (define iter (iterator '(10 (5 (1 ()(3 ()())) (6 ()())) (15 ()(16 () ())))))
  (and
   (equal? (iter) 1)
   (equal? (iter) 3)
   (equal? (iter) 5)
   (equal? (iter) 6)
   (equal? (iter) 10)
   (equal? (iter) 15)
   (equal? (iter) 16)
   (equal? (iter) #f)
   (equal? (iter) #f)))