Event are not retrieved by emitted() when using Collapse from BootstrapVue

[klak-bm]

Version

1.0.0-beta.16

Reproduction link

https://github.com/klak-bm/bv-collapse-problem/

Steps to reproduce

git clone https://github.com/klak-bm/bv-collapse-problem/ && cd bv-collapse-problem/ && npm i && npm test

What is expected?

First test should return emitted events but it does not.

What is actually happening?

0 event returned

---

I already tried in local with beta.20 but doesnt change anything.

The working test shows that instead of clicking on the button which triggers the "expand", if I force emitting the corresponding event the test is working (I expect another event to be emitted then).

At first, I thought the problem was coming from bootstrap-vue (and their collapse transition) but after discussing with their active members, they took a look and finally told me :
"The show should be emitted regardless of transition
The HTML already has the correct aria expanded and show class
Which makes me think, perhaps the test wrapper on the child component (b-collapse) isn't firing it's event on the test"

"This sounds like a potential Vue test utils bug to be honest"

[eddyerburgh]

Thanks for the detailed bug report, and sorry for the issues this has caused you.

Yes this is a bug with Vue Test Utils, and is part of a wider bug we have with asynchrnous DOM updates.

A temporary workaround if to run your tests asynchronously, without a transition stub:

let wrapper = mount(App, {
    sync: false,
    stubs: {
        'transition': false
    }
});

You'll need to edit your assertion to run in a timeout calback:

test('some test', (done) => {
    // ..
    setTimeout(() => {
        expect(wrapper.emitted().MyCompExpand).toBeTruthy();
        done()
    })
})

[mosinve]

wrapper.vm.$nextTick() instead setTimeout works also

[eddyerburgh]

In order to keep the issue tracker clean, I'm closing the original sync issue in favor of #676.

I'm working to find a solution to this bug, but it will be easier for me to manage other issues if there is only one open issue to track.