Right way to mock Ionic framework

I have a service called AlertService which has two properties of type Alert (of the Ionic framework). I want to implement tests for this service but I don't want to use the framework classes for simplification reasons. So I would like to mock the AlertController and Alert classes to test my AlertService. My idea would be to implement such a class in replacement of the Alert one (of Ionic):

class AlertMock {
    opts:       Object;
    presented:  boolean;

    constructor(opts) {
        this.opts       = opts;
        this.presented  = false;
    }

    present() {
        this.presented  = true;
    }

    dismiss() {
        this.presented  = false;
    }
}

How can I do that ? Knowing that my AlertService references the Alert class of Ionic.