Changes To Mounted Component Not Showing In Enzyme Even After Timeout

how can i test the child component has mounted. Please see the below implmentation.

i have an api call, until the data resolves it will show a loader then it will show the actual component.

Using mount i need to simulate a click on the child component also. What am i doing wrong here.

Please see the below snippet.

// App.js

import React, {Component, Fragment} from 'react'
import Child from './child'

class App extends Component{

  state = {
    data: null,
    enable: false
  }

  componentDidMount(){
    this.getData()
  }

  getData = async () => {
    const response = await fetch('http://www.example.com');
    const data = await response.json();
    this.setState({
      data
    })
  }

  _handleChildClick = () => {
    this.setState({
      enable: true
    })
  }

  render(){
    const {data, enable} = this.state
    if(!data){
      return (
       <div>
         Loading
       </div>
      )
    }else{
      <Fragment>
        <Child
         handleChildClick={this._handleChildClick}
        />
      </Fragment>
    }
  }
}


export default App


import React from 'react';

const child = () => {
  return(
    <div>
      <button
        className="toggle"
        onClick={props.handleChildClick}
      >
      Toggle
      </button>
    </div>
  )
}

export default child

// App.test.js

import React from 'react';
import {enzyme} from 'enzyme';
import App from './App';

describe("App test cases", () => {
  it('should trigger _handleChildClick', async () => {
    window.fetch = jest.fn().mockImplementation(() => ({
      status: 200,
      json: () => new Promise((resolve, reject) => {
        resolve(
            {
              name: "some data"
            }
        )
      })
    })) 
    const mountWrapper = await mount(<App />)
    mountWrapper.update()
    console.log("mountWrapper", mountWrapper.debug()) // showing the loader one
    setTimeout(() => {
      console.log("mountWrapper", mountWrapper.debug()) // nothing showing
      // expect(mountWrapper.find('.toggle').length).toEqual(1)
    },0)
  })
})

You have to update your enzyme wrapper inside the timeout.

import React from 'react';
import {enzyme} from 'enzyme';
import App from './App';

describe("App test cases", () => {
  it('should trigger _handleChildClick', async () => {
    window.fetch = jest.fn().mockImplementation(() => ({
      status: 200,
      json: () => new Promise((resolve, reject) => {
        resolve(
            {
              name: "some data"
            }
        )
      })
    })) 
    const mountWrapper = await mount(<App />)
    mountWrapper.update()
    console.log("mountWrapper", mountWrapper.debug()) // showing the loader one
    setTimeout(() => {

      //**An update required here
      mountWrapper.update();

      console.log("mountWrapper", mountWrapper.debug()) // nothing showing
      // expect(mountWrapper.find('.toggle').length).toEqual(1)
    },0)
  })
})

Live example created here: https://codesandbox.io/s/5083l6vmjk