Jest (JavaScript framework)

Jest[1] is a JavaScript testing framework maintained by Facebook, Inc. with a focus on simplicity. It works with projects using: Babel, TypeScript, Node.js, React, Angular, Vue.js and Svelte. It aims to work out of the box and config free.

Usage and examples

 
$ npm install --save-dev jest

For the following module, we will write a corresponding test case:

function sum(a, b) {
  return a + b;
}
module.exports = sum;

If the above file was named sum.js, we will write our test case in a file named sum.test.js for jest to automatically pick it up. The contents of the file will be: 

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

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

Then, from the command line, run the command

$ npm run test

This runs the test and outputs the corresponding result in your command line.

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See also

References
  1. "Jest Website".
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