How to do jest testing in react native?

user_8565241 0
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I have a simple code which I have written to test.

This is my App.js:

const App: () => React$Node = () => {

  function sum(a, b) {
     alert(a + b);
     return a + b;
  }

  return (
     <>
        <Button
          title="Sum"
          onPress={() => {sum(1,2)}}
        />
       
  );

This is my App-test.js in the __tests__ folder:

import 'react-native';

const sum = require('../App');

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3);
});

When I run npm test I get this error TypeError: sum is not a function. Can anyone help.

Note: When I run it on my android phone it works properly and shows 3 in the alert box.

react-native jestjs
1 Answers

It's because you are importing sum from your App file but it is not an exported method the way you wrote it.

You can do something like this:

export const sum = (a, b) => {
   alert(a + b);
   return a + b;
}

export const App = () => (
   <Button
      title="Sum"
      onPress={() => {sum(1,2)}}
   />
);

And use it like this in your test file:

import { sum } from '../App'

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3);
});

It's not particularly linked to React Native since you're only trying to test a specific method, which can be use with any framework.

user_55679360
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