fix: do not exit when only unref'd timer is present in test code

lib/runnable.js

@@ -20,6 +20,8 @@ var setTimeout = global.setTimeout;
 var clearTimeout = global.clearTimeout;
 var toString = Object.prototype.toString;
 
+var MAX_TIMEOUT = Math.pow(2, 31) - 1;
+
 module.exports = Runnable;
 
 /**
@@ -95,8 +97,7 @@ Runnable.prototype.timeout = function (ms) {
   }
 
   // Clamp to range
-  var INT_MAX = Math.pow(2, 31) - 1;
-  var range = [0, INT_MAX];
+  var range = [0, MAX_TIMEOUT];
   ms = utils.clamp(ms, range);
 
   // see #1652 for reasoning
@@ -233,11 +234,8 @@ Runnable.prototype.clearTimeout = function () {
  */
 Runnable.prototype.resetTimeout = function () {
   var self = this;
-  var ms = this.timeout();
+  var ms = this.timeout() || MAX_TIMEOUT;
 
-  if (ms === 0) {
-    return;
-  }
   this.clearTimeout();
   this.timer = setTimeout(function () {
     if (self.timeout() === 0) {

test/integration/fixtures/options/timeout-unref.fixture.js

@@ -0,0 +1,3 @@
+it('unrefs a timeout', function(done) {
+  setTimeout(done, 10).unref();
+});

test/integration/options/timeout.spec.js

@@ -83,4 +83,15 @@ describe('--timeout', function () {
       }
     );
   });
+
+  it("should complete tests having unref'd async behavior", function(done) {
+    runMochaJSON('options/timeout-unref', ['--timeout', '0'], function(err, res) {
+      if (err) {
+        done(err);
+        return;
+      }
+      expect(res, 'to have passed').and('to have passed test count', 1);
+      done();
+    });
+  });
 });

test/unit/runnable.spec.js

@@ -702,6 +702,7 @@ describe('Runnable(title, fn)', function () {
       runnable.timeout(10);
       runnable.resetTimeout();
       runnable.timeout(0);
+      runnable.run();
       setTimeout(function () {
         expect(runnable.timedOut, 'to be', false);
         done();