I want to write unit tests with sinon for async.parallel.

My code looks like this:

async.parallel(async.reflectAll(fns), function (err,res) {
   console.log("err", err) // Nothing shows here
}
);

I tried to stub the async.parallel using sinon like this:

const stubbedModule = sinon.stub(require.cache[require.resolve('async')],
  'parallel', () => {
    return 'I\'m stubbed!';
  });

But that doesn't work. When I consoled inside the body of the async.parallel function, nothing goes there, no error, no results. I am so confused on how to stub the parallel method of async.