const localStorageMock = (function() { let store = {}; return { store, getItem: function(key) { return store[key]; }, setItem: function(key, value) { store[key] = value; }, clear: function() { store = {}; } }; })(); Object.defineProperty(window, 'Storage', { value: localStorageMock }); Object.defineProperty(window, 'localStorage', { value: localStorageMock });