How to add custom message to Jest expect?

Question

Image following test case:

it(\'valid emails checks\', () => {
  [\'abc@y.com\', \'a@b.nz\'/*, ...*/].map(mail => {
    expect(isValid(mail)).toBe(true);
          


        

Answer 1

Another way to add a custom error message is by using the fail() method:

it('valid emails checks', (done) => {
  ['abc@y.com', 'a@b.nz'/*, ...*/].map(mail => {
    if (!isValid(mail)) {
      done.fail(`Email '${mail}' should be valid`)
    } else {
      done()
    }
  })
})