How to add custom message to Jest expect?

Question

Image following test case:

it('valid emails checks', () => {   ['[email protected]', '[email protected]'/*, ...*/].map(mail => {     expect(isValid(mail)).toBe(true);   }); }); 

I would like to add auto-generated message for each email like Email '[email protected]' should be valid so that it's easy to find failing test cases.

Something like:

// .map(email => expect(isValid(email), `Email ${email} should be valid`).toBe(true); 

Is it possible in Jest ?

In Chai it was possible to do with second parameter like expect(value, 'custom fail message').to.be... and in Jasmine seems like it's done with .because clause. But cannot find solution in Jest.

Answer 1

You try this lib that extends jest: https://github.com/mattphillips/jest-expect-message

test('returns 2 when adding 1 and 1', () => {   expect(1 + 1, 'Woah this should be 2!').toBe(3); });