#lang racket/base

(require racket/match)
(require rackunit)
(require "os-big-bang.rkt")

(provide check-message-handler)

(define (flatten-transition t)
  (if (transition? t)
      (transition (transition-state t) (transition-actions t)) ;; autoflattens
      (transition t '()))) ;; wrap for convenient comparison

(define (check-message-handler mh initial-w message final-w expected-actions)
  (match-define (on-message pattern handler) mh)
  (check-true (pattern message) "Message-handler pattern did not match message provided")
  (define v (match (handler message initial-w)
	      [(? transition? t) t]
	      [new-w (transition new-w '())]))
  (check-equal? (flatten-transition v) (transition final-w expected-actions)
		"Produced world-and-actions did not match expected world-and-actions"))