Let's write a test for a function that adds two numbers in sum.js
file:
const sum = (a, b) => a + b
export default sum
Create a file named sum.test.js
which contains actual test:
import sum from './sum'
test('adds 1 + 2 to equal 3', () => {
expect(sum(1, 2)).toBe(3)
})
And then add the following section to your package.json
:
{
"scripts": {
"test": "jest"
}
}
Finally, run yarn test
or npm test
and Jest will print a result:
$ yarn test
PASS ./sum.test.js
✓ adds 1 + 2 to equal 3 (2ms)