Tests using createLocalVue() display warning (rc.20)

Describe the bug

Tests using bootstrap-vue and createLocalVue() output the following warning

[BootstrapVue warn]: Multiple instances of Vue detected!
See: https://bootstrap-vue.js.org/docs#using-module-bundlers

The test code looks like:

  beforeEach(() => {
    const localVue = createLocalVue();
    localVue.use(BootstrapVue);

    wrapper = mount(SomeComponent, { localVue });
  });

Expected behavior

Tests run successfully without warnings.

Versions

Libraries:

• bootstrap-vue: 2.0.0-rc.20
• bootstrap: 4.3.1
• vue: 2.6.10
• jest: 24.8.0
• vue-jest: 3.0.4
• @vue/test-utils: 1.0.0-beta.29

Environment:

Jest

Possible solution?!

The issue can be fixed by moving the localVue.use() statement from the test file

  beforeEach(() => {
    const localVue = createLocalVue();
    sectionPallet = mount(SectionPallet, { localVue });
  });

to the jestSetup.js.

import Vue from 'vue';
//...
Vue.use(BootstrapVue);

Now the tests run successfully. But the question is: Is that intended?

[tmorehouse]

Version 2.0.0-rc.21 has been released

[tmorehouse]

The warnings should not cause tests to fail (but will place console warns in your test logs)

Adding the Vue.use in jestSetup.js would include the full library in each test, rather than testing for just the certain components in our test suites.

You can disable BootstrapVue warns by setting process.env.BOOTSTRAP_VUE_NO_WARN = true before running your tests.

https://bootstrap-vue.js.org/docs/misc/settings#disabling-bootstrapvue-console-warnings

You can also set up a console.warn mock to trap the warns (which we have done in some of our tests):

  beforeAll(() => {
    // Prevent multiple Vue warnings in tests
    jest.spyOn(console, 'warn').mockImplementation(() => {})
    // Install plugin after we have trapped console.warn
    localVue.use(toastPlugin)
  })

  afterAll(() => {
    console.warn.mockClear()
  })