universe restart test, bug from Marco

(cherry picked from commit 7df831feec)

collects/2htdp/tests/universe-restart.rkt

@@ -0,0 +1,45 @@
+#lang racket
+
+(module drop-on-message racket
+  (require 2htdp/universe 2htdp/image)
+  
+  (define (u)
+    (universe 0
+              (on-new (lambda (u w) (make-bundle (+ u 1) '() '())))
+              (on-msg (lambda (u w m) (make-bundle (- u 1) '() (list w))))
+              (state #t)))
+  
+  (define (w n)
+    (big-bang 3
+              [to-draw (lambda (w) (overlay (text (number->string w) 22 'black) (circle 100 'solid 'red)))]
+              [on-tick (lambda (w) (if (<= w 1) (make-package 0 n) (- w 1)))]
+              [register LOCALHOST]
+              [name n]))
+  
+  (launch-many-worlds (u) (w "one") (w "two")))
+
+(require (submod "." drop-on-message))
+
+(module drop-bad racket
+  (require 2htdp/universe 2htdp/image)
+  
+  (define *world* #false)
+
+  (define (u)
+    (universe '()
+              (on-new (lambda (u w) (make-bundle (cons w u) '() '())))
+              (on-msg (lambda (u w m) 
+                        ;; set *world* to the first world that comes around, reuse
+                        (unless *world* (set! *world* w))
+                        (make-bundle u '() (list *world*))))))
+  
+  (define (w n)
+    (big-bang 3
+              [to-draw (lambda (w) (overlay (text (number->string w) 22 'black) (circle 100 'solid 'red)))]
+              [on-tick (lambda (w) (if (= w 1) (make-package 0 n) (- w 1)))]
+              [register LOCALHOST]
+              [name n]))
+  
+  (launch-many-worlds (u) (w "one") (w "two") (w "three")))
+
+; (require (submod "." drop-bad))