How mock constructor variables in react js test cases file?

user_7908077 0
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I am having the class named SelectedValues like below which has a global variable "this.others"

export default class SelectedValues extends React.Component {

  /* istanbul ignore next */
  constructor(props) {
    super(props);
    this.renderOption = this.renderOption.bind(this);
    this.deselectOption = this.deselectOption.bind(this);
    this.others= [];
    this.state = {
      typedText: '',
      index: null,
      typedContext: '',
    };
  }
  
 deselectOption(event, option, index){
    const selectedOptions = _.clone(this.props.value);
    let selectedOptionsValue = _.split(selectedOptions.value, ';');

    selectedOptionsValue.splice(index, 1);
    console.log(this.others);
    let othersIndex =  this.others[index].OtherIndex;

    let typedUpdateContext = '';
    if(othersIndex === 0){
      let temp = this.others.find(item => item.OtherIndex === 1);
      typedUpdateContext = temp? temp.value : '';
    }

    _.remove(this.others, { 'key': option + index });
  }

  render(){
     return(...);
  }
}

The code is working fine but when I ran the test file by using npm run test for the above "deselectOption" method and I am getting error like below TypeError: Cannot read property 'OtherIndex' of undefined

Later I found the issue is causing because of this.others(which is a global variable) and it is an empty array. So how to mock "this.others" before i call deselectOption Method in test file.

I am new in writing test cases for unit test cases. Please help me to resolve this error.

Thank you in advance.

reactjs mocha.js unit-testing
1 Answers

Thanks @slideshowp2 for providing suggestion, I am able to mock the data in my test file from after getting a component instance.

So others is a constructor variable. To mock this variable, I followed the below process and it worked to me.

const wrapper = shallow(<SelectedValues value={input} onChange={onChangeSpy} />);
    const instance = wrapper.instance();
  //Below i am mocking "others" variable
   instance['others'] = [
    {
      'key':'Add 10 statements0',
      'value':'Add 10 statements',
      'OtherIndex': null
    },
    {
      'key':'Verify bank statements1',
      'value':'Verify bank statements',
      'OtherIndex': null
    },
    {
      'key':'Other2',
      'value':'loan',
      'OtherIndex': 1
    }
   ];
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