Testing window.onbeforeunload

Setting onbeforeunload to null helps here:

window.onbeforeunload = null;

Still curious if you have some other suggestions,

Thanks

For reference, this worked for me. Angular service:

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

And onto unit testing with Jasmine:

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

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