Remove duplicate code in test file (#1976)

packages/node/test/machine/integration/message-router.ts

@@ -1,34 +1,8 @@
+import { Deferred } from "../../../src/deferred";
 import { Opcode } from "../../../src/machine";
 
 import { MiniNode } from "./mininode";
 
-/// copied from node
-/// see also: https://twitter.com/joseph_silber/status/809176159858655234
-class Deferred<T> {
-  private internalPromise: Promise<T>;
-  private internalResolve!: (value?: T | PromiseLike<T>) => void;
-  private internalReject!: (reason?: any) => void;
-
-  constructor() {
-    this.internalPromise = new Promise<T>((resolve, reject) => {
-      this.internalResolve = resolve;
-      this.internalReject = reject;
-    });
-  }
-
-  get promise(): Promise<T> {
-    return this.internalPromise;
-  }
-
-  resolve = (value?: T | PromiseLike<T>): void => {
-    this.internalResolve(value);
-  };
-
-  reject = (reason?: any): void => {
-    this.internalReject(reason);
-  };
-}
-
 export class MessageRouter {
   private nodesMap: Map<string, MiniNode>;
   private deferrals: Map<string, Deferred<any>>;