How to create a test for a function with a service inside?

Question

I have the code below and managed to create a test for it, when it enters error 400 and 200. However, I can’t get the test to enter the catch.

I’m using Mocha and Chai.

myController.approve = (request, response) => {
    let { id, text } = request.body;

    if (!myController.idValidId(id)) {
        response.status(400).send();
        return;
    }

    myService.approve(id, text)
    .then(() => {
        response.send(200);
    })
    .catch(error => {
        response.status(error.response.status).json({
            approved: false,
            error: "Erro ao aprovar documento",
        });
    });
};

My test:

describe('POST document', function () {
    it('should return OK for the document', function (done) {
        request(server)
        .post('/my-url')
        .send({
            id: 1,
            text: 'Teste de Observação',
        })
        .then(function(res){
            expect(res.statusCode).to.equal(200);
            done();
        })
    });

    it('should return ERROR for document ID invalid', function (done) {
        config.mockDocumentApproval();

        request(server)
        .post('/my-url')
        .send({
            id: 'not-a-number-valid',
            text: 'Teste de Observação',
        })
        .then(function(res){
            expect(res.statusCode).to.equal(400);
            done();
        })
    });

    it('should return error for document', function (done) {
        // Erro ao entrar no tach
    });
});

How do I get my test into error?

Answer 1

I don’t know the details of the implementation but it would be a way to force the error. For the examples of my attempts I will highlight only the excerpt I modified in relation to your code:

One way to try to force the 500 would be to send the id a negative number.

.send({
   id: -1,
   text: 'Teste de Observação',
})

A second way is to send the number 0.

.send({
   id: 0,
   text: 'Teste de Observação',
})

Another attempt is to send a special character

.send({
       id: '#@',
       text: 'Teste de Observação',
})

Another possibility is to send null or empty.

.send({
       id: null,
       text: 'Teste de Observação',
})
//----------------
.send({
       id: '',
       text: 'Teste de Observação',
})

Another possibility is not to send.

.send({
       text: 'Teste de Observação',
})

One thing we could try was to send a giant number (which force the overflow to the types long and int

.send({
       id: 99999999999999999999999999999999999999999999999999999999999999999999999,
       text: 'Teste de Observação',
})

If you still can’t, a possibility for the 500 is to make 2 consecutive registrations with the same id, this will force the database to error 500 if it is validating single id. Primary key validation (Constraint UNIQUE).

I hope somehow an error occurs 500.