Test a callback Function using jest and enzyme in ReactJS?

Question

I am new to TDD and I want to test my callback function in my Age component : my Age.js file is following :

import React, { Component } from "react";
import { connect } from "react-redux";
import actions from "../../actions";
import TextFieldComponent from "../Module/TextFieldComponent";

export class Age extends Component {

  ageValueCallBack = age => {
    console.log("value is : ", age);
    this.props.selectAgeAction(age)
  };

  render() {
    const props = {
      onChange: this.ageValueCallBack,
      hintText : 'Eg. 25',
      floatingLabelText: "Age(Years)",
      value : (this.props.usersData) ? this.props.usersData.basic.age : null
    };
    return <TextFieldComponent {...props} />;
  }
}

function mapStateToProps({ usersData }) {
  return {
    usersData
  };
}

export default connect(mapStateToProps, {
  selectAgeAction: actions.selectAgeValue
})(Age);

where my TextFieldComponent is following :

import TextField from "material-ui/TextField";

const TextFieldComponent = props => {
  return (
    <TextField
        onChange={(event, string) => {
        props.onChange(string)
      }}
      floatingLabelText={props.floatingLabelText || "floatingLabelText"}
      value={props.value || null}
      hintText={props.hintText || "hintText will be here"}
      autoFocus ={true || props.autoFocus}
    />
  );
};

I want to test ageValueCallBack function of Age component but I'm not getting any particular method to reach there.

Any insight will be helpful.

Thanks..

Answer 1

With enzyme you can trigger the onChange event on the TextFieldComponent using simulate('change', {}, 'someString'). The selectAgeAction in your Age.js needs to be a spy created with jest.fn():

const selectAgeAction = jest.fn()
const component = shallow(<Age selectAgeAction={selectAgeAction} />)
component.find('TextField').simulate('change', {}, '10')
expect(selectAgeAction).toHaveBeenCalledWith('10')