测试数组时 Jest 预期 0 收到 1

我正在尝试测试以查看在执行此测试时未输入任何输入时它们是否为无列表

App.test.tsx

describe('Should test empty array on onSubmit method',() => {
  it('should test empty array  onSubmit method', ()=>{
    const component = shallow(<App/>)
    const form = component.find('Form').at(0);
    const preventDefault = jest.fn();
    // const items = ['Learn react', 'rest', 'go out'];
    // component.setState({
    //  currentTask:"test-task",
    //  tasks:[...items, 'test-task']
    // })

    // form.simulate('submit', { preventDefault });
    // expect(preventDefault).toBeCalled();
    // form.props().onSubmit();
    form.simulate('submit', {preventDefault})
    expect(component.state().tasks.length).toBe(0);

  })
})

但是我收到这个错误

● 应该在 onSubmit 方法上测试空数组 › 应该在 onSubmit 方法上测试空数组

expect(received).toBe(expected) // Object.is equality

Expected: 0
Received: 1

我注意到我有读取这个的 linting 错误

Property 'tasks' does not exist on type 'Readonly<{}>'.

在这条线上

expect(component.state().tasks.length).toBe(0);

我应该改变什么才能通过？

我引用了类似于这个问题的东西

预期数组但在 Jest 中收到数组

但该解决方案对我不起作用。

应用程序.tsx

import React from 'react';
import logo from './logo.svg';
import Form from './Form';
import './App.css';
// we need an interface to be able to use the state properties, if not error.
// the same rule applies when using props
// so here we call Istate
interface IState {
  currentTask: string;
  tasks: Array<string>;
}

export default class App extends React.Component<{}, IState>{
  constructor(props: {}){
    super(props);
    this.state = {
      currentTask: "",
      tasks:[]
    }
  }

  // when using e.preventDefault in typescript, or any paramater, it has to be followed
 //  by the following any, array, string, etc. in this case we use any

  handleSubmit(e: any){
    e.preventDefault();
    this.setState({
      currentTask: "",
      tasks: [...this.state.tasks, this.state.currentTask]
    }, () => {
      console.log(this.state.tasks)
    })


  }

  onChange = (e: any) => {
    e.preventDefault();
    this.setState({
      currentTask: e.target.value
    })

  }

  render(){
    return (
      <div className="App">
        <h1 className="sampleh1">React Typescript Todo</h1>

        <Form 
          onSubmit={(e)=> this.handleSubmit(e)}
          currentTask={this.state.currentTask}
          onChange={this.onChange}  
        />
      </div>
    );

  }
}

边注

如果我更改代码

expect(component.state().tasks.length).toBe(0);

至

expect(component.state().tasks).toHaveLength(0);

我明白了，我很困惑，因为它们在数组中没有值，那么为什么它接收 1 而不是 0 ？？？

 Received array:  [""]