angular mock sessionStorage

import { TestBed } from '@angular/core/testing';
import { ReloadService } from './reload.service';

window.onbeforeunload = jasmine.createSpy();

describe('ReloadService', () => {
  let service: ReloadService;
  let mockSessionStorage: { [key: string]: string } = {};

  beforeEach(() => {
    mockSessionStorage = {};

    const mock = {
      getItem: (key: string): string | null => mockSessionStorage[key] || null,
      setItem: (key: string, value: string): void => {
        mockSessionStorage[key] = value;
      },
      removeItem: (key: string): void => {
        delete mockSessionStorage[key];
      },
      clear: (): void => {
        mockSessionStorage = {};
      },
    };

    spyOn(sessionStorage, 'getItem').and.callFake(mock.getItem);
    spyOn(sessionStorage, 'setItem').and.callFake(mock.setItem);
    spyOn(sessionStorage, 'removeItem').and.callFake(mock.removeItem);
    spyOn(sessionStorage, 'clear').and.callFake(mock.clear);

    TestBed.configureTestingModule({
      providers: [ReloadService],
    });
    service = TestBed.inject(ReloadService);

    spyOn(service, 'performReload').and.callFake(() => {});
  });

  it('should set sessionStorage and reload the page if not reloaded before', () => {
    service.reload();
    expect(sessionStorage.setItem).toHaveBeenCalledWith(
      'isPageReloaded',
      'true'
    );
    expect(service.performReload).toHaveBeenCalled();
  });

  it('should not reload the page if already reloaded', () => {
    sessionStorage.setItem('isPageReloaded', 'true');
    service.reload();
    expect(service.performReload).not.toHaveBeenCalled();
  });
});

Angular reload service

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root',
})
export class ReloadService {
  private storageKey = 'isPageReloaded';

  reload(): void {
    if (!sessionStorage.getItem(this.storageKey)) {
      sessionStorage.setItem(this.storageKey, 'true');
      this.performReload();
    }
  }

  performReload(): void {
    location.reload();
  }
}