How do I test props passed to child component using Enzyme Shallow?

Question

I'm having an issue testing my component which thinly wraps the Material-UI autocomplete. In my test, I'd like to view the props being passed to , but my console statement is an empty object. I'm using Enzyme's shallow method to render this. Here's my code:

const underlineFocusStyle = {
    display: 'block',
    height: '100%',
    outline: 'none',
    position: 'relative', 
    padding: '0px', 
    width: '100%',
    border: 'none',
    backgroundColor: 'rgba(0, 0, 0, 0)',
    cursor: 'inherit',
    opacity: '1'
};

export class MyAutoComplete extends React.Component {
    render() {
        let { muiTheme, forceOpenOnFocus, ...propsToApply } = this.props;
        propsToApply.underlineFocusStyle = underlineFocusStyle;

        if (forceOpenOnFocus) {
            if (!propsToApply.filter) {
                propsToApply.filter = ((searchText, key) => {
                    return searchText === '' || AutoComplete.defaultProps.filter(searchText, key);
                });
            }
        }
        return <AutoComplete name={'autocomplete'} {...propsToApply} />;
    }
}

MyAutoComplete .propTypes = {
    muiTheme: PropTypes.object,
    forceOpenOnFocus: PropTypes.bool
}

export default muiThemeable()(MyAutoComplete );

And my test:

describe('LLamasoftAutoComplete', () => {
    const muiTheme = getMuiTheme();
    const shallowWithContext = (node) => shallow(node, {context: {muiTheme}});

    it('should pass in ', () => {
        const wrapper = shallowWithContext(
            <LLamasoftAutoComplete 
                muiTheme={muiTheme} 
                forceOpenOnFocus={true}
                dataSource={['One', 'Two', 'Three']} />
        );

        console.log(wrapper.find('AutoComplete').props()); //  is {}

        expect(true).toBe(false);
    });
});

Answer 1

As you may already know, shallow rendering a component "one level deep". Also, I assume that you are familiar with the concept of HOC.(Higher-Order components). Your MyAutoComplete wrapped with muiThemeable HOC. So shallow rendering only render the muiThemeable and it doesn't render what you have inside MyAutoComplete's render method. Because those are deep in the component tree more than one level.

To avoid this problem we usually test undecorated component; the original component before wrapping with HOC. So we need to export both decorated and undecorated component from the file, decorated one as a default export and undecorated one as a named export.

export default muiThemeable()(MyAutoComplete);
export { MyAutoComplete };

Now you can import undecorated one and test it. In you case, you don't actually need to render it with context since you no longer have muiThemeable in your component, which depends on context. So your test becomes simpler.

import { MyAutoComplete as LLamasoftAutoComplete} from './your/file/location'

describe('LLamasoftAutoComplete', () => {
    const muiTheme = getMuiTheme();

    it('should pass in ', () => {
        const wrapper = shallowWithContext(
            <LLamasoftAutoComplete 
                muiTheme={muiTheme} 
                forceOpenOnFocus={true}
                dataSource={['One', 'Two', 'Three']} />
        );

        console.log(wrapper.find('AutoComplete').props());

        expect(true).toBe(false);
    });
});

Read answers to this question for more info: How to test decorated React component with shallow rendering