sinon_test.js

var testRetryCounter = 0;
var assert = chai.assert;

$.ajax = function(opts) {
  testRetryCounter++;
  setTimeout(opts.error, 0);
};

describe('Data', function() {
  describe('#sendData()', function() {

    var clock;

    before(function () { clock = sinon.useFakeTimers(); });
    after(function () { clock.restore(); });

    it('should retry 3 times before quitting', function() {
      var p = new PersonalData();
      p.sendData();
      assert.equal(testRetryCounter, 1);

      clock.tick(3000);
      assert.equal(testRetryCounter, 2);

      clock.tick(3000);
      assert.equal(testRetryCounter, 3);

    });
  });
});