(define-library (euler interest-test)
  (export run-tests)
  (import (scheme base) (scheme process-context) (euler interest))
  (begin
    (define (test expect expr)
      (cond
       ((not (or (equal? expect expr)
                 (and (or (inexact? expect) (inexact? expr))
                      (let ((a (min expect expr))
                            (b (max expect expr)))
                        (< (abs (/ (- a b) b)) 0.000001)))))
        (write-string "FAIL\n")
        (exit 1))))
    (define (run-tests)
      (test 2.0 (compound-interest 1 1.0 1 1))
      (test 2.25 (compound-interest 1 1.0 1 2))
      (test 2.4414 (compound-interest 1 1.0 1 4))
      (test 2.71828 (compound-interest 1 1.0 1)))))