Angular Unit Testing - Cannot read properties of undefined (reading 'size') NgRx

I get an error about my spec file unit test without success to solve, the error display when I run npm test, on karma chrome:

enter image description here

agent.service.spec.ts:

import { HttpClientTestingModule } from '@angular/common/http/testing';
import { TestBed } from '@angular/core/testing';
import { RouterTestingModule } from '@angular/router/testing';
import { MemoizedSelector, Store } from '@ngrx/store';
import { MockStore, provideMockStore } from '@ngrx/store/testing';
import * as fromGrid from './../grid/store/grid.reducer';
import { GridActions } from './../grid/store/grid.actions';
import { AgentService } from './agent.service';
import { GridSizeEnum } from '../models/enums/GridSize';
describe('AgentService', () => {
let agentService: AgentService;
let mockStore: MockStore<fromGrid.State>;
let mockGridSizeSelector: MemoizedSelector<fromGrid.State, GridSizeEnum>;
let size: GridSizeEnum = GridSizeEnum.GRID_1
beforeEach(() => {
TestBed.configureTestingModule({
imports: [
HttpClientTestingModule,
RouterTestingModule
],
providers: [
AgentService,
provideMockStore({}),
],
});
agentService = TestBed.get(AgentService);
mockStore = TestBed.get(Store);
mockGridSizeSelector = mockStore.overrideSelector(fromGrid.getGridSize, size);
});
it('should return the default state', () => {
const action = {} as GridActions;
const state = fromGrid.reducer(fromGrid.initialState, action);
expect(state).toBe(fromGrid.initialState);
});
it('should be created', () => {
expect(agentService).toBeTruthy();
});
afterEach(() => {
})
});

agent.service.ts :

the constructor part-

  constructor(private http: HttpClient,
private router: Router,
private store: Store<fromRoot.State>,
private gridStore: Store<fromGrid.State>,
private commandWebSocket: CommandWebsocketService,
private logService: LogService) {
this.commandWebSocket.connect();
this.commandWebSocket.messages$.subscribe((data) => {
this.commandWebsocketData(data);
});
this.store.pipe(select(fromGrid.getGridSize), takeUntil(this.destroyed$)).subscribe((size) => {
if (size) {
this.gridSize = size;
}
});
this.gridStore.pipe(select(fromGrid.getGridVideoStreamIDs, this.gridSize), takeUntil(this.destroyed$)).subscribe(data => {
if (data && data.length) {
this.gridStreamIDs = data;
const byPassCpuIdsCopy = this.byPassCpuIds;
this.byPassCpuIds = [];
this.gridStreamIDs.filter((dta) => {
this.byPassCpuIds[dta] = byPassCpuIdsCopy[dta];
});
}
});
}

grid.reducer.ts :

export const getGridSize = createSelector(
getGridFeatureState,
state => state.size
);

This error appears a lot in another case, when I have subscribe to specific selector at constructor() or at ngOnInit() (if it component unit test ).

For solution i tried to initial the state in spec file, see above in agent.service.spec... but it isn't solved.
Need your help, thanks!

How can i solve this error:

Cannot read properties of undefined (reading 'size')

You need to initialize your store:

provideMockStore({
grid: {     // assuming 'grid' is your feature key
size: 5
}
})

also need to initialize the selectors in provideMockStore():

provideMockStore({
initialState: fromGrid.initialState,
selectors: [
{
selector: fromGrid.getGridSize,
value: GridSizeEnum.GRID_1
}
]
}),