fix(accordion): collapsed class not correct

[ExFlo]

fixes #2553

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[pkozlowski-opensource]

Couldn't we add assert to https://github.com/ExFlo/ng-boostrap/blob/e1064feca33b001b9cad323edb4f5ffbb0c0373a/src/accordion/accordion.spec.ts#L37 instead of writing whole new test?

The advantage is that it would be verified with all the existing tests.

[ExFlo]

I can but we are not going to test that the class is present in case of close panels just that it is not present in case of open ones. Do we want only this?

[pkozlowski-opensource]

@ExFlo I was more thinking of sth like:

panelsTitles.map((titleEl: HTMLButtonElement) => {
   const isAriaExpanded = titleEl.getAttribute('aria-expanded') === 'true';
   const isCSSCollapsed = titleEl.classList.contains('collapsed');
   return isAriaExpanded === !isCSSCollapsed ? isAriaExpanded : fail('inconsistent state');
});

not well thought-through, just a rough idea...

[ExFlo]

So we just test that collapsed is correctly removed, but not that it is in place the first time right?

[pkozlowski-opensource]

During the first time rendering we should have:

• isAriaExpanded=false
• isCSSCollapsed=true

Given this the isAriaExpanded === !isCSSCollapsed condition should be true and the return value false.

If the class wouldn't be here initially we would get:

• isAriaExpanded=false
• isCSSCollapsed=false

and the isAriaExpanded === !isCSSCollapsed test would fail breaking the test. So I believe that the case of initial display would be covered as well.

But hey, this is just a rough idea, feel free to adapt / discard.

[ExFlo]

right I missed the use case of the function. Thx