(define-record-class (account <account>) ()
     ((balance 0) (transactions '())))

;; never mind the silly tests
(define acc (make-account 2))
(test-assert (account? acc))
(test 2 (account-balance acc))
(test '() (account-transactions acc))
(account-balance-set! acc 9)
(test 9 (slot-value acc 'balance))