Angular 角度业力测试对象：无法读取属性'；未定义'；未定义的

我一直被困在这个问题上，我现在不知道如何解决或找到解决方案

我有一个角度服务，我使用它从我的NGXS商店的购物清单中获取一天的条目

但是，它在ng测试中抛出一个错误，表示“无法读取未定义的属性‘未定义’”

服务中的代码如下所示，相当简单

getDataFromStore(daySelected: string): DailyShopList {
    return this.store.selectSnapshot<DailyShopList>(
        state => state.shoppingList.dailyEntries[daySelected] <--- issue is here
    );
}

我错过了什么

多谢各位

describe('ShoppingListService', () => {
    let service: ShoppingListService;
    const data = {
        state: {
            shoppingList: {
                dailyEntries: {
                    mon: {},
                    tue: {},
                },
            },
        },
    };

    beforeEach(() => {
        TestBed.configureTestingModule({
            imports: [
                HttpClientTestingModule,
                NgxsModule.forRoot([MyNGXSstate]),
            ],
        });
        service = TestBed.inject(ShoppingListService);
        const store: Store = TestBed.get(Store);

        spyOn(store, 'selectSnapshot').and.returnValue(data); // trying to mock data from store
    });

    it('should be created', () => {
        expect(service).toBeTruthy();
    });
});