How to use with Nuxt.js

[rubenmoya]

Hello!

I'm trying to use vue-testing-library with Nuxt.js and I'm facing a problem with asyncData not being called.

I've been reading for a while, and some people call wrapper.vm.$options.asyncData() manually, but that feels super dirty to me, also I don't think vm is available in vue-testing-library

Any idea of how can I do it? I ran out of ideas to be honest.

I've seen @afontcu post about testing api calls but it uses the created life cycle method

Thank you!

[afontcu]

Hi Rubén! This is quite a good question 🤔

I can't think of a way to test a page with asyncData (or fetch), since they are not part of the usual component lifecycle. AFAIK same issue should happen in Vue Test Utils.

Not sure there's a way for us to fix this, to be honest. You could try and use tools such as nuxt.renderRoute as described here.

If you come up with any good idea, please do share it! 🙌

[rubenmoya]

To be honest I didn't came up with a good solution, I just went ahead and used Cypress 🤷‍♂

[afontcu]

Thanks for the update! Looks like the way I would've followed, too :)

[Martin7mind]

i did this and it kind of works.. but is there a better solution now?

export const mountWithAsyncData = async (component, options) => {
  let data
  if (component.asyncData) {
    const asyncDataReq = component.asyncData({ app: { $axios: axios } })
    await options.respondToAsyncData()
    data = await asyncDataReq
  }

  return mount(component, {
    data: () => data,
    ...options
  })
}

[damafeez]

This is what I came up with, I might end up converting it into a tiny package later.

import { mount } from '@vue/test-utils'

export async function mountWithAsyncData(
  component,
  { asyncDataContext, ...options } = {},
) {
  const initialData = options.data === 'function' ? options.data() : null
  if ('data' in options && initialData === null)
    throw new Error('data should be a function that returns an object')
  if (typeof component.asyncData === 'function') {
    const data = await component.asyncData(asyncDataContext)
    options.data = () => ({ ...(initialData || {}), ...(data || {}) })
  }
  return mount(component, options)
}

notices how it merges asyncData with existing data in options

Then you can use like, assuming your asyncData function returns { myAsyncData,}

 test('asyncData is merged to VM data', async () => {
  const $emit = jest.fn()
  const wrapper = await mountWithAsyncData(Page, {
    asyncDataContext: {
      $axios: {
        get() {
          return {
            data: myAsyncData,
          }
        },
      },
      $route: mockedRoute,
    },
    mocks: {
      $auth: authMock,
    },
  })
  expect(wrapper.vm.myAsyncData).toBe(myAsyncData)
})

[msmsimondean]

Here's what I've used:

test/nuxtMountUtils.js

import { mount, shallowMount } from '@vue/test-utils'

export async function shallowMountWithFetch(component, options) {
  options.mountFunction = shallowMount
  return await mountWithFetch(component, options)
}

export async function mountWithFetch(
  component,
  { mountFunction, fetchGlobal, fetchMocks, fetchContext, ...options } = {}
) {
  if (!mountFunction) {
    mountFunction = mount
  }
  const wrapper = mountFunction(component, options)
  const fetch = wrapper.vm.$options.fetch
  if (typeof fetch !== 'function') {
    throw new TypeError('fetch should be a function')
  }
  const thisArg = { ...wrapper.vm.$data, ...fetchMocks }
  const originalGlobal = {}
  for (const key of Object.keys(fetchGlobal)) {
    originalGlobal[key] = global[key]
    global[key] = fetchGlobal[key]
  }
  await fetch.apply(thisArg, [fetchContext])
  for (const key of Object.keys(fetchGlobal)) {
    global[key] = originalGlobal[key]
  }
  delete thisArg.$config
  wrapper.setData(thisArg)
  return wrapper
}

Example Usage

import Index from '@/pages/index.vue'
import { mountWithFetch } from '~/test/nuxtMountUtils'

describe('Index', () => {
  const bodyJson = { /* fake response body goes here */ }
  const fetch = jest.fn(() => {
    expect(url).toBe('https://example.com/something')
    return Promise.resolve({
      json: () => Promise.resolve(bodyJson),
    })
  })
  let wrapper
  const createWrapper = async () => {
    wrapper = await mountWithFetch(Component, {
      fetchGlobal: {
        fetch,
      },
    })
  }

[aldarund]

There should a way to call vm methods in testing-library to properly work with nuxt or it should have something like nuxt option that will call fetch automatically like created

[afontcu]

Hi! Thanks for your input

There should a way to call vm methods in testing-library

I don't think this is likely to happen, as it might lead to tests that rely on implementation details.

it should have something like nuxt option that will call fetch automatically like created

This is interesting and worth exploring! Do you have an idea about what the API should look like?

[aldarund]

@afontcu there basically two hooks that is executed and needed.
fetch and asyncData https://nuxtjs.org/docs/2.x/features/data-fetching

[afontcu]

What could the API look like?

render(Component, { fetch, asyncData })

where fetcth and asyncData are functions that we run appropriately?

[aldarund]

what for pass them ? I mean its look like more what i offered as first option e.g. to call vm method manually but via different syntax.
What i mean by automatic nuxt support is that render should just call fetch automatically if it exist on component and same for asyncData, but for asyncData it should also merge returned result into component data.

[afontcu]

Oh right, I see, forget my last post. I have some doubts (does it mean render is going to return a Promise?), but I'm willing to add this to the library. Would you like to open a PR? 🙌