add spreadfactor test

test/test.js

@@ -157,5 +157,30 @@ async.series([
     });
 
     ports.dev2.write(`send${message}\n`);
-  });
+  }, "round-trip message");
+
+  test(function(t) {
+    t.plan(2);
+
+    var sf = 9;
+    var msg = `sf${sf}\n`;
+
+    testSetSpreadFactor(ports.dev1);
+    testSetSpreadFactor(ports.dev2);
+
+    function testSetSpreadFactor(port) {
+      var buf = "";
+
+      port.on("data", function onData(c) {
+        buf += c.toString();
+
+        if(buf.indexOf(`spreadfactor: ${sf}`) !== -1) {
+          t.pass("spreadfactor set");
+          port.removeListener("data", onData);
+        }
+      });
+
+      port.write(msg);
+    };
+  }, "spreadfactor");
 });