#lang racket (require 2htdp/universe) (require 2htdp/image) (define (f x) (cond [(= x 0) (circle 10 'solid 'red)] [(= x 1) (circle 20 'solid 'red)] [else (error txt)])) (define txt "all questions were #f") (with-handlers ([exn? (lambda (e) (unless (string=? (exn-message e) txt) (raise e)))]) (big-bang 0 (on-tick add1) (to-draw f)) (error 'error-in-draw "test failed"))