Cannot clear timer error with sinon/mocha

[kennydude]

I'm dealing with an issue which is cropping up 50% of the time on our tests using Sinon, Mocha and Testem.

It's seemingly random all of the tests will fail starting with:

 Uncaught Error: Cannot clear timer: timer created with setTimeout() but cleared with clearInterval()

And the stack trace (even with source-map-support) doesn't give any clue as to what is causing the issue.

[mantoni]

The error message means that you have something like this in your code:

var timer = setTimeout(/*...*/);
// ...
clearInterval(timer);

Detecting this kind of wrong timer usage was added to the fake timer library.
I suggest you're greping through your codebase and replace the clearInterval with a clearTimeout call.

It's unclear to me why this happens only 50% of the time, but failing on this kind of timer usage is intentional and not a bug in Sinon.

[kennydude]

No instances of setTimeout or clearInterval exist in the code, it's all handled by underscore :/

[mantoni]

Maybe underscore clears timers with clearInterval?

[kennydude]

Nope :/ There's no mention of clearInterval in the source code

[fatso83]

It would help a lot if you could actually make a little snippet of code displaying the issue. This does indeed seem like a bug in client code.

I'd suggest firing up Chrome, setting a breakpoint at the relevant line in sinon, and see where the stack trace leads you.

Re the relevant line, I'd checkout the vicinity of line 971:

$ ack -C10 'Cannot clear timer'
pkg/sinon-1.17.0.js
961-        if (typeof timerId === "object") {
962-            timerId = timerId.id;
963-        }
964-
965-        if (clock.timers.hasOwnProperty(timerId)) {
966-            // check that the ID matches a timer of the correct type
967-            var timer = clock.timers[timerId];
968-            if (timerType(timer) === ttype) {
969-                delete clock.timers[timerId];
970-            } else {
971:                throw new Error("Cannot clear timer: timer created with set" + ttype + "() but cleared with clear" + timerType(timer) + "()");
972-            }

[kennydude]

The funny thing is this only ever shows up on CircleCI for me so I can't do that. I did a search for clearTimeout and it could be Bootstrap causing issues.

So I might have cleared it by disabling it, hopefully.

[pabigot]

I've also encountered this and finally tracked it down: if clearInterval is called with an undefined interval sinon appears to record it as a timer rather than an interval.

Reproducible with mocha 4.0.1 and sinon 4.1.1 and this code under Node.js 4.5:

'use strict';

const sinon = require('sinon');

describe('Test', function() {
  let clock;
  beforeEach(() => {
    clock = sinon.useFakeTimers(24 * 60 * 60 * 1000);
  });
  afterEach(() => clock.restore());
  it('should work', function() {
    const id = setInterval(() => null);
    clearInterval(id);
  });
});

producing:

 lilith[49]$ node_modules/.bin/mocha sinon872.js 


  Test
    1) should work


  0 passing (9ms)
  1 failing

  1) Test
       should work:
     Error: Cannot clear timer: timer created with setTimeout() but cleared with clearInterval()
      at clearTimer (node_modules/sinon/node_modules/lolex/src/lolex-src.js:359:19)
      at Object.clearInterval (node_modules/sinon/node_modules/lolex/src/lolex-src.js:504:16)
      at target.(anonymous function) (node_modules/sinon/node_modules/lolex/src/lolex-src.js:406:34)
      at Context.<anonymous> (sinon872.js:13:5)

[mroderick]

@pabigot thank you for the test case ❤️

Would you consider making a PR to fix it also?

[fatso83]

@mroderick, @pabigot created #1611, which I closed after moving it to sinonjs/fake-timers#138. FYI

[pabigot]

Fix submitted as sinonjs/fake-timers#139.

[mroderick]

@pabigot Thank you 👍

[fatso83]

Fix released as 4.1.2