Vue action test with API call

api_action.spec.js

// the action
[actionTypes.ACTION_SET_FAV_ELEM] (context) {
  return APIAdapter.services.fetchFavElem()
    .then((response) => {
      context.commit(mutationTypes.MUTATION_SET_FAV_ELEM, response)
      resolve(true)
    }).catch((error) => {
      context.commit(mutationTypes.MUTATION_SET_FAV_ELEM, undefined)
      reject(error)
    })
  },

// the tests
it('should invoke mutation to set the favourite element if the API call is succcessful', done => {
  const expectedPayload = 'AAAAA'
  const fetchFavElemStub = sinon.stub(APIAdapter.services, 'fetchFavElem').resolves(expectedPayload)
  
  testAction(actions[actionTypes.ACTION_SET_FAV_ELEM], null, {}, [
    { type: mutationTypes.MUTATION_SET_FAV_ELEM, payload: expectedPayload }
  ], () => {
    fetchFavElemStub.restore()
    done()
  })
})

it('should invoke mutation to set the favourite element as undefined if the API is not succcessful', done => {
  const fetchFavElemStub = sinon.stub(APIAdapter.services, 'fetchFavElem').rejects()
  
  testAction(actions[actionTypes.ACTION_SET_FAV_ELEM], null, {}, [
    { type: mutationTypes.MUTATION_SET_FAV_ELEM, payload: undefined }
  ], () => {
    fetchFavElemStub.restore()
    done()
  })
})