How to test props after being assigned to new variable

Question

I'm trying to test an if condition with props. It works fine if I pass in this.props.thingToTest but if I assign something like const propsVariable = this.props.thingToTest and test the if condition, I won't get code coverage.

I've tried passing in the const as props in my shallow wrapper, or declaring the const in the test but it still doesn't see it.

Component code:

render() {
    const propsVariable = this.props.thingToTest;

    if (this.props.otherThingToTest === 'test') {
      return <Component />;
    } else {
      if (propsVariable) {
        return <OtherComponent />;
      }
    }
  }

Test code:

const props = {
  propsVariable: {}
}

it('tests else condition in render method', () => {
    const wrapper = shallow(<OriginalComponent {...props} />);
    const instance = wrapper.instance();
    jest.spyOn(instance, 'render');
    instance.render();
    expect(instance.render).toHaveBeenCalled();
  });

I expect the else case to get hit and return <OtherComponent /> but it doesn't hit the else case at all.

If I put otherThingToTest in the props object in my test it'll hit the first if case fine, but because my other prop thingToTest is assigned to a variable, it won't hit the else case and I'm not sure how to test that.

anonymous anonymous · Accepted Answer · 2019-04-20T05:02:08

Since you have not passed thingToTest props to the component in Test code, propsVariable will be assigned undefined.

const propsVariable = this.props.thingToTest; // propsVariable = undefined

That's why code will not take the if path inside the else block and hence return <OtherComponent />; statement will not covered.

So you need to just pass thingToTest props to the component in Test code and it will work fine.

const props = {
  thingToTest: 'someValue'
  // passing propsVariable: {} won't work
  // since it will be available as 
  // "this.props.propsVariable" inside the 
  // component 
}

Note: else case will hit if you don't pass otherThingToTest props.

How to test props after being assigned to new variable

1 Answers