Testing error handling?

This just a question, not a real issue, but in your section on Error Handling you have the following example:

function* checkout(getState) {

  while( yield take(types.CHECKOUT_REQUEST) ) {
    try {
      const cart = getState().cart
      yield call(api.buyProducts, cart)
      yield put(actions.checkoutSuccess(cart))
    } catch(error) {
      yield put(actions.checkoutFailure(error))
    }
  }
}

How would I go about testing the error case? I’d like to test what happens when the function passed in the call statement rejects its Promise or throws an Error.

The best thing I can think of is trying to mock the call function to just throw an error, but that seems messier than I’d like. Any ideas? Thanks!

[yelouafi]

The best thing I can think of is trying to mock the call function to just throw an error

You don’t have to mock, yield call(...) doesn’t execute anything, to test the generator you provide it with dummy responses. To simulate a promise rejection, call throw on the iterator

const cart = {}
const getState = () => ({cart})
const iterator = checkout(getState)

assert.deepEqual(iterator.next().value, take(types.CHECKOUT_REQUEST))
assert.deepEqual(iterator.next(actions.checkoutRequest()).value, call(api.buyProducts, cart) )
// simulate a promise rejection
assert.deepEqual(iterator.throw('error').value, put(actions.checkoutFailure('error')))

[KamuelaFranco]

Can this go in the docs? Please?