add exchange test

this ensure continuous rx is reenabled

test/test.js

@@ -183,4 +183,34 @@ async.series([
       port.write(msg);
     };
   }, "spreadfactor");
+
+  test(function(t) {
+    t.plan(4);
+
+    var i = 0;
+
+    async.doUntil(function(done) {
+      var write = ports["dev" + (1 + i % 2)];
+      var read = ports["dev" + (1 + (i + 1) % 2)];
+
+      var buf = "";
+      var msg = `tick${i}`;
+
+      read.on("data", function onData(c) {
+        buf += c.toString();
+
+        if(buf.indexOf(msg) !== -1) {
+          t.pass("got message " + i);
+
+          read.removeListener("data", onData);
+
+          done(null);
+        }
+      });
+
+      write.write(`send${msg}\n`);
+    }, function() {
+      return ++i > 5;
+    })
+  }, "exchange");
 });