New test case

syndicate/test/core/spawn-and-send.rkt

@@ -0,0 +1,46 @@
+#lang imperative-syndicate/test-implementation
+;; Test the "spawn and send" idiom, where event ordering is exploited
+;; to ensure a listener is ready by the time a sent message is ready
+;; for delivery.
+;;
+;; I'm still not 100% convinced this is the way things really ought to
+;; work. In old-Syndicate, the assertion of interest was exactly the
+;; same as installation of a handler-procedure, and the one could not
+;; occur before the other. Here, the installation of the handler
+;; happens *before* declaration of interest: in particular, no
+;; separate `#:assertions` clause is needed to ensure routing of the
+;; `(item)` message to the newly spawned `server` process. In
+;; old-Syndicate, the spawner of `server` would have to include
+;; `(observe (item))` in order for the `(item)` not to be dropped by
+;; the `server`. Perhaps this new-Syndicate should include handlers in
+;; patches, somehow, so that the declaration-of-interest and
+;; installation-of-handler move together? Then the `#:assertions`
+;; would really be `#:transient-endpoints` and would include `(assert
+;; ...)` and `(on ...)`, which is a bit jolly strange, so perhaps the
+;; current behaviour is better after all?
+
+(test-case
+    [(message-struct item ())
+     (message-struct server-present (how))
+     (spawn #:name 'main
+            (on (message (item))
+                (printf "Item received by main\n"))
+            (during (server-present $how)
+              (on-start (printf "Server is present: ~a\n" how))
+              (on-stop (printf "Server is not present: ~a\n" how)))
+            (on-start (printf "Spawning server\n")
+                      (spawn #:name 'server
+                             #:assertions [(server-present 'outside)]
+                             (assert (server-present 'inside))
+                             (on (message (item))
+                                 (printf "Item received by server\n")))
+                      (printf "Sending item\n")
+                      (send! (item))))]
+  no-crashes
+  (expected-output (list "Spawning server"
+                         "Sending item"
+                         "Server is present: outside")
+                   (set "Item received by main"
+                        "Item received by server")
+                   (list "Server is present: inside"
+                         "Server is not present: outside")))