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

you can use this: (you can define it inside the test)

      expect.extend({
ToBeMatch(expect, toBe, Msg) {  //Msg is the message you pass as parameter
    const pass = expect === toBe;
    if(pass){//pass = true its ok
        return {
            pass: pass,
            message: () => 'No ERRORS ',
          };
    }else{//not pass
        return {
            pass: pass,
            message: () => 'Error in Field   '+Msg + '  expect  ' +  '  ('+expect+') ' + 'recived '+'('+toBe+')',
          };
    }
},  });

and use it like this

     let z = 'TheMassageYouWantWhenErrror';
    expect(first.name).ToBeMatch(second.name,z);