问角/ ngrx存储4:在组件测试中未初始化状态

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TypeError: undefined is not an object (evaluating 'state.search.results')

StoreModule.forRoot ({reducers}),
...
store = TestBed.get (Store);
spyOn (store, 'dispatch').and.callThrough ();

import * as fromSearch from './search/search-reducer';
export interface State {
  search: fromSearch.State;
}

export const reducers = {
  search: fromSearch.reducer
};

export interface State {
  searchTerms: string;
  results: [];
  limit: SearchLimit;
}
// Imported: initialState & initalSearchLimitState
const initialState: State = {
  searchTerms: '',
  results:     [initialState],
  limit:       initalSearchLimitState
};

export function reducer (state = initialState, action: SearchActions.All): State {
  switch (action.type) {
    case SearchActions.SEARCH: {
      return {
        ...state,
        searchTerm: action.payload
      };
    }

    case SearchActions.SEARCH_SUCCESS: {
      return {
        ...state,
        results: action.payload
      };
    }

    case SearchActions.SEARCH_LIMIT_EXCEEDED: {
      return {
        ...state,
        limit: action.payload
      };
    }

    default: {
      return state;
    }
  }
}

this._searchService.search (query).subscribe (results => {
    this._store.dispatch (new SearchActions.SearchSuccess (results.data));
});