How to use enzyme for react-native with jest - react-native

Question

I have followed –or tried to– several posts on how to do it, including the airbnb enzyme's guide for (separatedly) react-native and jest. (E.g: https://medium.com/#childsmaidment/testing-react-native-components-with-enzyme-d46bf735540#.6sxq10kgt, https://blog.callstack.io/unit-testing-react-native-with-the-new-jest-i-snapshots-come-into-play-68ba19b1b9fe#.4iqylmqh5 or How to use Jest with React Native)
But I keep getting lots of warnings (I have multiple set of concurrent tests) whenever I try to render (not mount, it crashes) any native component. Warnings are always about a native prop not being recognised.
Warning: Unknown props `focus`, `secureTextEntry` on <TextInput> tag. Remove these props from the element.
in TextInput (created by TextInput)
in TextInput (created by PasswordInput)
Anyone who has a set up working, recognises how to remove the warning or how to solve it?
Thanks

Answer 1

So I know this is a bit old but I was having issues with Jest, Enzyme, and React Native and I found this post - hopefully this solution will help.
To start with - Enzyme doesn't support mounting React Native and only supports shallow rendering. This wasn't good enough for me as I needed end-to-end tests from the component to the api which lead me to react-native-mock-render. What this does is allow us to run react native inside a browser environment which let's us test using Enzyme - all the calls for React Native and the components work as you would expect.
To set this up you'll need to install JSDOM, react-native-mock-render, Enzyme 3.0+, and Jest 20.0.0+. And then inside your jest setup file (which is specified in your package.json) include the following code:
const { JSDOM } = require('jsdom');
const jsdom = new JSDOM();
const { window } = jsdom;
function copyProps(src, target) {
const props = Object.getOwnPropertyNames(src)
.filter(prop => typeof target[prop] === 'undefined')
.map(prop => Object.getOwnPropertyDescriptor(src, prop));
Object.defineProperties(target, props);
}
global.window = window;
global.document = window.document;
global.navigator = {
userAgent: 'node.js',
};
copyProps(window, global);
// Setup adapter to work with enzyme 3.2.0
const Enzyme = require('enzyme');
const Adapter = require('enzyme-adapter-react-16');
Enzyme.configure({ adapter: new Adapter() });
// Ignore React Web errors when using React Native
console.error = (message) => {
return message;
};
require('react-native-mock-render/mock');
And that's it - you're all setup to mount components in Enzyme and test them.
If you want to see a full sample check out react-native-mock-render-example. This is working with React 16, React Native 0.51, and Enzyme 3.2.

Answer 2

In order to unit test your component with jest you can use enzyme-to-json
npm install --save enzyme-to-json
then your test would look like this:
import { shallow } from 'enzyme';
import { shallowToJson } from 'enzyme-to-json';
import MyComponent from './MyComponent';
it('should render component', => {
expect(shallowToJson(shallow(<MyComponent />))).toMatchSnapshot();
});

Answer 3

I'm not sure regarding your case with react-native.
I can share my case of using jest + enzyme with standard react.
When I needed to test some component and isolate it from others I used jest.mock, e.g.
jest.mock('../ComponentToBeMocked', () => {
return () => null;
});
Initially I found examples when the second argument (a function) should return just a string representing a name of the mocked component. But in that case I saw that distracting Unknown props warning.