我是 react/redux 世界的新手，我使用此代码创建了 redux todo 应用程序，现在我想为它编写测试，我创建了以下规范：

import {expect} from 'chai'
import todoApp from '../src/reducers'
import {setVisibilityFilter} from '../src/actions'

describe('reducer', ()=> {
    it('Set correctly visibility filter', ()=>{
        const setVisibilityFilterAction = setVisibilityFilter('SHOW_ALL')
        const initialState={};
        const nextState= todoApp(initialState, setVisibilityFilterAction)
        const expectedState ={
                todos:[],
                visibilityFilter:'SHOW_ALL' 
            }
        expect(nextState).to.equal(expectedState);
    })
})  

但是断言失败了，错误是：

AssertionError: expected { Object (todos, visibilityFilter) } to equal { Object (todos, visibilityFilter) }
      + expected - actual

试图打印对象并且它们（expectedState和nextState）都具有相同的数据：

{
   todos:[],
   visibilityFilter: "SHOW_ALL"
}

为什么失败了？