Must be able to disable heartbeats for testing

imperative/distributed/heartbeat.rkt

@@ -2,17 +2,24 @@
 
 (provide heartbeat)
 
+(module+ for-testing
+  (provide heartbeats-enabled?))
+
 (require "wire-protocol.rkt")
 
 (require/activate imperative-syndicate/drivers/timer)
 
 (define-logger syndicate/distributed)
 
+(define heartbeats-enabled? (make-parameter #t))
+
 ;; TODO: move heartbeats to transport level, and use separate transport-activity timeouts from
 ;; message-activity timeouts. Using message-activity only has problems when messages are large
 ;; and links are slow. Also, moving to transport level lets us use e.g. WebSocket's ping
 ;; mechanism rather than a message-level mechanism.
 (define (heartbeat who send-message teardown)
+  (cond
+    [(heartbeats-enabled?)
      (define period (ping-interval))
      (define grace (* 3 period))
 
@@ -37,4 +44,7 @@
 
      (lambda ()
        (schedule-next-ping!)
-    (last-received-traffic (current-inexact-milliseconds))))
+       (last-received-traffic (current-inexact-milliseconds)))]
+    [else
+     (log-syndicate/distributed-debug "Peer ~v heartbeats disabled" who)
+     void]))

imperative/test/distributed/nesting-confusion.rkt

@@ -5,6 +5,9 @@
 (require imperative-syndicate/distributed)
 (require imperative-syndicate/distributed/internal-protocol)
 
+(require (submod imperative-syndicate/distributed/heartbeat for-testing))
+(heartbeats-enabled? #f)
+
 (assertion-struct researcher (name topic))
 
 (define test-address (server-loopback-connection "test"))

imperative/test/distributed/observation-visibility.rkt

@@ -5,6 +5,9 @@
 (require (only-in imperative-syndicate/lang activate))
 (require imperative-syndicate/distributed)
 
+(require (submod imperative-syndicate/distributed/heartbeat for-testing))
+(heartbeats-enabled? #f)
+
 (assertion-struct presence (who))
 
 (define test-address (server-loopback-connection "test"))