Sinon: force callback call

Question

I'm testing a function with this code:

return new Promise((ok, fail) => {
  this.repository.findById(id, (error, result) => {
    if (error)
      return fail(error);
    ok(result);
  });
});

I want to test the path of the fail, i.e., when the findById method calls the callback with an error. I'm using sinon to generate a stub for my repository and its findById method, but I don't know how to force the stub to call the callback with the desired parameters

Anybody did something like that before?

Thanks

Answer 1

With Sinon 2, you can use the callsFake method of a stub:

sinon.stub(repository, 'findById').callsFake((id, callback) =>
    callback(new Error('oops'))
);

See Sinon 2 documentation: http://sinonjs.org/releases/v2.1.0/stubs/