fix: test

packages/core/cyclist.mjs

@@ -227,6 +227,7 @@ const processMessage = (message) => {
   }
 };
 
+if (typeof self !== 'undefined') {
   self.onconnect = function (e) {
     // the incoming port
     const port = e.ports[0];
@@ -236,6 +237,7 @@ self.onconnect = function (e) {
     });
     port.start(); // Required when using addEventListener. Otherwise called implicitly by onmessage setter.
   };
+}
 
 function createClock(
   callback, // called slightly before each cycle