Testing function chains using Sinon.JS

Question

How can I test a function like the following using Sinon.JS?

export function getToken(done) {
  const kc = Keycloak(config)
  kc.init({ onLoad: 'login-required' })
    .success(authenticated => {
      authenticated ? done(null, kc.token) : done(new Error('Some error!'), null)
    })
    .error(() => {
      done(new Error('Some error'), null)
    })
}

I tried doing something like the following, to no avail:

it('should return access_token', () => {
    const mockKeycloak = sinon.stub(Keycloak, 'init').returns({
      success: () => (true)
    })
    getToken(function () {})
    expect(mockKeycloak.callCount).to.equal(1)
  })

Basically Keycloak from keycloak-js is an IIFE but even after trying to stub the Keycloak object on the window reference, I can't make it to work.

Answer 1

For anyone who lands here, this is what I did:

Since Keycloak is an IIFE, it overrides the stubbed object once we do

const kc = Keycloak(config)

Therefore I just exported this object kc from the source and stubbed the init method on it and it worked just fine!