Running jest with bootstrap-vue

Question

I've been working with vuejs and bootstrap-vue lately. Decided to add unit testing to my project.

I'm not realy familiar with unit testing so I'm trying anything I could find to understand how it works.

Login.specs.js

import { shallowMount, mount } from '@vue/test-utils'
import Login from '@/components/auth/Login.vue'

describe('Login.vue', () => {
  it('is a Vue instance', () => {
   const wrapper = mount(Login, {
    mocks: {
     $t: () => 'Connexion' // i18N
    }
   })
  const h2 = wrapper.find('h2')
  expect(h2.text()).toBe('Connexion')
 })
})

Login.vue

<b-row align-h="center">
 <b-col class="text-center">
  <h2>{{ $t('login.connection') }}</h2>
 </b-col>
</b-row>

Everything seems ok with the test. But I got these wannings and could find a way to actualy fix it.

[Vue warn]: Unknown custom element: - did you register the component correctly? For recursive components, make sure to provide the "name" option.

[Vue warn]: Unknown custom element: - did you register the component correctly? For recursive components, make sure to provide the "name" option.

So I looked around and it seems like I need to add these child components to the father.

Here is the documentation for these components.

I'm also adding my config files (There're the same as the vue-cli 3 generates them)

jest.congif.js

module.exports = {
  moduleFileExtensions: [
  'js',
  'jsx',
  'json',
  'vue'
 ],
 transform: {
  '^.+\\.vue$': 'vue-jest',
  '.+\\.(css|styl|less|sass|scss|png|jpg|ttf|woff|woff2)$': 'jest- transform-stub',
  '^.+\\.jsx?$': 'babel-jest'
 },
 moduleNameMapper: {
  '^@/(.*)$': '<rootDir>/src/$1'
 },
 snapshotSerializers: [
  'jest-serializer-vue'
 ],
 testPathIgnorePatterns: [ //I've added this one, not sure if usefull
  '<rootDir>/node_modules'
 ],
 testMatch: [
  '**/tests/unit/**/*.spec.(js|jsx|ts|tsx)|**/__tests__/*.(js|jsx|ts|tsx)'
 ]
}

Answer 1

It is also possible to stub components like

const wrapper = mount(Login, {
  mocks: {
    $t: () => 'Connexion' // i18N
  },
  stubs: {
    BCol: true
  }
});

Answer 2

If you're adding bootstrap vue as a global plugin:

Vue.use(BootstrapVue);

Then in your tests, you're likely going to want to follow this tip:

https://vue-test-utils.vuejs.org/guides/common-tips.html#applying-global-plugins-and-mixins

Which outlines how you can use the createLocalVue() and set it up with the same global config as your app:

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

// create an extended `Vue` constructor
const localVue = createLocalVue()

// install plugins as normal
localVue.use(BootstrapVue)

// pass the `localVue` to the mount options
mount(Component, {
  localVue
})

Then your components should be registered properly-