fix: Jest tests are inaccurate since v.0.23.0

[tommycoppers]

🐛 The bug
Upgrading to version v.0.23.0 (https://github.com/nuxt-community/composition-api/releases/tag/0.23.0) breaks testing with Jest. Namely, the setup() function in a component is never being called. Note that the application works as expected. It's only the tests that are showing odd behavior.

My assumption is that the 'auto-mock' is not working as expected, outside a Nuxt context. Hoping someone can help!

I've followed the release notes to update my app to do the following:

nuxt.config

FROM:

  buildModules: ['@nuxtjs/composition-api'],

TO:

  buildModules: ['@nuxtjs/composition-api/module'],

jest.config

FROM:

moduleNameMapper: {
   // ...
  '@nuxtjs/composition-api': '@nuxtjs/composition-api/entrypoint',
},

TO:

moduleNameMapper: {
   // ...
},

With the upgrade, nothing in the setup() method is being executed, however, the component still compiles. If i reorganized a dummy component to use a data prop, for example, the tests would attach the value to mounted compnent's vm property.

🛠️ To reproduce
Steps to reproduce the behavior:

1. Install version v0.22.4
2. Add the composition api to your buildModules ( buildModules: ['@nuxtjs/composition-api'],)
3. Add the entrypoint to the moduleNameMapper ( '@nuxtjs/composition-api': '@nuxtjs/composition-api/entrypoint',)
4. Write a dummy component with a setup function that returns an object with some key/value pairs (`setup(){ return {foo:'bar'} }
5. Write a dummy test for the component. Console log a value that was returned by the components setup() method. Example

import { mount, createLocalVue } from '@vue/test-utils';
import foobar from './foobar.vue';

const localVue = createLocalVue();
describe('foobar', () => {
  test('renders correctly', () => {
    const wrapper = mount(foobar, {
      localVue,
    });

    console.log(`>>> wrapper.vm.foo <<<\n`, wrapper.vm.foo);

    expect(wrapper.vm.foo).toBe('bar')
  });
});

6. Observe a passing test and a printed value of 'bar'
7. Install version v0.23.0
8. Update the buildModules in nuxt.config (buildModules: ['@nuxtjs/composition-api/module'],)
9. Remove the moduleNameMapper from jest.config
10. Repeat steps 4-5 (or just rerun the test)
11. Observe test fail and a printed value of undefined

🌈 Expected behaviour
I expected that the tests that passed prior to the upgrade would also pass after the upgrade.