How to fail cypress test from inside the Promise.prototype.catch() block?

Question

I'm using a node library to execute api calls for test data setup and teardown. The library works as follows:

someApiServiceObject
.executeApiCall({... parameters})
.then(doSomethingWithResults())
.catch(() => { 
  // Here I would like to fail the test as something has gone wrong
})

If the request fails for some reason, I only learn about it by the Promise returning from executeApiCall function being rejected - hence the catch block.

But if I put throw new Error(); into the catch block or remove the catch block, I can see the (uncaught exception) Error: in the cypress console, but the test still passes.

Can someone advise me on how this case should be handled correctly?

The test:

it('List projects', () => {
    projectsApi.projectsList({})
      .then(() => {
        cy.log('Success');
      }).catch(() => {
        throw new Error();
      });
  });

Answer 1

If you call someApiServiceObject.executeApiCall({...parameters}) in a task (since it's a node library), you should just be able to return the promise and Cypress handles failing the test. Don't catch() within the task.

module.exports = (on, config) => {
  on('task', {
    api(parameters) {
      return someApiServiceObject
        .executeApiCall({... parameters})
        .then(doSomethingWithResults())   
    },
  })
}

If that fails, follow this pattern Return number of files in the folder

module.exports = (on, config) => {
  on('task', {
    countFiles(folderName) {
      return new Promise((resolve, reject) => {
        someApiServiceObject
          .executeApiCall({... parameters})
          .then(doSomethingWithResults())
          .then((results) => resolve(results))
          .catch((err) => reject(err))
        })
      })
    },
  })
}

---

From comments, I think there's a assumption being made that .executeApiCall() must be returning a promise, but that may not be the case.

For example cy.get(...) has a .then(...) method, but it does not return a promise, it just has a .then() method.

If .executeApiCall() does actually return a promise, the first example is all you need. If it does not, you need to wrap the code.

Cypress will recognise a promise returned from a task, and use resolve or reject accordingly.