mocha-aura-callback-sample.js

poolForChanges(so) {
    // Prepare environment
    const component = componentFactory({});
    const callback = sinon.spy();
    // Invoke component helper method
    helper.poolForChanges(component, callback);
    // helper method should call another helper method.
    // It's second parameter has a callback we are going to test
    expect(helper.pullSummary).to.have.been.called;
    const [{args: [,pullTicketSummaryCallback]}] = helper.pullSummary.getCalls();

    // Invoke pullSummary's callback we extracted from stubbed pullSummary helper method 
    pullSummaryCallback(so);
    // An outer callback should not called because inside pullSummaryCallback helper method has setTimeout() call
    expect(callback).not.to.have.been.called;
    this.clock.tick(751);
    // Outer callback will be called after a timeout in a synchronous manner
    expect(callback).to.have.been.called;
}