How to test return function value

Question

How can I test the return value for this function ?

handleValidatePassword = (confirmPassword) => {
    const { newPassword } = this.props;
    if (newPassword !== confirmPassword) {
      return <FormattedMessage id="some value" />;
    }
  }

I need to check if the returned value of this function is the expected one if condition is right:(FormattedMessage return span with value === id)

<span> some value </span>

i'm using shallow from enzyme for test

Your question is a bit unclear. What are you using to render your component in the tests (Could it be enzyme?) — litelite
– litelite, Commented Aug 2, 2019 at 12:03
In function put console.log(changePass.alerts.notMatch); before return. — Bhawana
– Bhawana, Commented Aug 2, 2019 at 12:13

Maciej Trojniarz · Accepted Answer · 2019-08-02 13:39:04Z

1

I would personally use enzyme-matchers if you use jest or jasmine f.e. https://github.com/FormidableLabs/enzyme-matchers/blob/master/packages/jest-enzyme/README.md#tocontainreact

import { shallow } from 'enzyme' 
import Element from './yourpath'

const wrapper = shallow(<Element />); // mount/render/shallow when applicable

//as shallow renders only one level of children components
expect(wrapper).toContainReact(<FormattedMessage id="some value" />);

//or if you want to test actually the span element you should use mount
const wrapper2 = mount(<Element />);
expect(wrapper).toContainReact(<span> some value </span>);

answered Aug 2, 2019 at 13:39

Maciej Trojniarz

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7 Comments

Denys Klymenko Over a year ago

does not work because <FormattedMessage> does not exist when the component is mounted, I have a condition inside the function, so I need to check that the function will return if the condition is met correctly, but thanks for this information, this will help me in the future. I need test just that function will return

Denys Klymenko Over a year ago

For example -- ` wrapper.instance().handleValidatePassword = jest.fn(); wrapper.instance().handleValidatePassword.mockReturnValue(<span> changePass.alerts.notMatch </span>);` But this does not work to

Maciej Trojniarz Over a year ago

Can you share component code where you are using this function? Is this condition in code depends on the state of component? If so then you can use setState in the tests f.e. like here

Denys Klymenko Over a year ago

Can I verify that this function will return? As if it is independent of components and other things

Denys Klymenko Over a year ago

or maybe I can somehow check if the condition works (example: newPassword !== confirmPassword)

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