start test suite for file/gif

This test belongs in a "draw-test" package, which doesn't exist yet,
because the old drawing tests also rely on a GUI; I'll fix that
eventually.

gui-test/tests/gracket/gif.rkt

@@ -0,0 +1,10 @@
+#lang racket/base
+(require file/gif
+         rackunit)
+
+(define g (gif-start (open-output-bytes) 10 10 0 #f))
+(check-equal? #t (gif-stream? g))
+(check-equal? #t (image-ready-gif-stream? g))
+(check-equal? #t (image-or-control-ready-gif-stream? g))
+(check-equal? #t (empty-gif-stream? g))
+