Experimenting with Jasmine unit testing for the `window.onbeforeunload` event

I've been struggling with writing unit tests that keep failing. Do you have any suggestions on the correct approach?

show(contactId: string, phoneNumber: string, contactType: string, section: string, memberId: string) {
        this.$window.onbeforeunload = () => "";
        $('.disabledcalldialog').on("click", e => {
            this.$window.alert('Please close call dialog and try.');
            e.preventDefault();
        });

This is a snippet from my spec file:

beforeEach(() => {
        inject(($rootScope: ng.IScope, $window) => {
    spyOn($window, 'onbeforeunload');
            $(window).trigger('onbeforeunload');
  });
  it('should be able to call when changing URL', () => {
        
        expect($window.onbeforeunload).toHaveBeenCalled();

Karma keeps giving me an error message saying "TypeError: Unable to get property 'onbeforeunload' of undefined or null reference";

javascriptangularjsunit-testingfrontendkarma-jasmine

Answer №1

Ready to serve you:

setUpBeforeunload(): void {
  window.addEventListener('beforeunload', this.closeConnection);
}

Time for unit testing using Jasmine:

describe('setUpBeforeunload', () => {
  it('will establish window eventListener', () => {
    spyOn(window, 'addEventListener');
    service.setUpBeforeunload();
    expect(window.addEventListener).toHaveBeenCalledWith('beforeunload', service.closeConnection);
  });

  it('should trigger closeConnection()', () => {
    spyOn(service, 'closeConnection');
    service.setUpBeforeunload();
    window.dispatchEvent(new Event('beforeunload'));
    expect(service.closeConnection).toHaveBeenCalled();
  });
});

Answer №2

Are you familiar with this method:

$window.trigger('onbeforeunload');

as an alternative to: 

$(window).trigger('onbeforeunload');

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