expect(() => {
      queue.schedule(() => {
        results.push(1);
      });

      queue.schedule(() => {
        throw new Error('bad');
      });
    }).to.throw(Error, 'bad');

 it('should schedule things recursively', () => {
   let call1 = false;
   let call2 = false;
   (queue as QueueScheduler).active = false;
   queue.schedule(() => {
     call1 = true;
     queue.schedule(() => {
       call2 = true;
     });
   });
   expect(call1).to.be.true;
   expect(call2).to.be.true;
 });

 setTimeout(() => {
   queue.schedule(() => {
     results.push(2);
     done();
   });
 }, 0);

 queue.schedule(() => {
   call1 = true;
   queue.schedule(() => {
     call2 = true;
   });
 });