fix: don't depend on private node api for Timeout wrapper

NODE-2460

Author: mbroadst

lib/core/topologies/shared.js

@@ -213,10 +213,18 @@ function Interval(fn, time) {
 
 function Timeout(fn, time) {
   var timer = false;
+  var func = () => {
+    if (timer) {
+      clearTimeout(timer);
+      timer = false;
+
+      fn();
+    }
+  };
 
   this.start = function() {
     if (!this.isRunning()) {
-      timer = setTimeout(fn, time);
+      timer = setTimeout(func, time);
     }
     return this;
   };
@@ -228,7 +236,6 @@ function Timeout(fn, time) {
   };
 
   this.isRunning = function() {
-    if (timer && timer._called) return false;
     return timer !== false;
   };
 }

test/unit/core/replset/utils.test.js

@@ -0,0 +1,16 @@
+'use strict';
+const Timeout = require('../../../../lib/core/topologies/shared').Timeout;
+const expect = require('chai').expect;
+
+describe('', function() {
+  it('should detect when a timer is finished running', function(done) {
+    let timeout;
+    function timeoutHandler() {
+      expect(timeout.isRunning()).to.be.false;
+      done();
+    }
+
+    timeout = new Timeout(timeoutHandler, 100);
+    timeout.start();
+  });
+});