when used with a sticky footer layout.
Adds visual test for affix with sticky footer.

Closes #15694.
Refs #15032.

Otherwise, the test doesn't properly fail when the fix is reverted.

Closes #16142 by merging it.

Closes #16219.

Closes #16151 by merging a rebased version of it that adds docs and 1 more assertion.

Closes #16039.

as this breaks keyboard navigation for radio button toggles (see
https://github.com/twbs/bootstrap/issues/16223)

Valid:

    function a() {}

Invalid:

    function a () {}

Currently, auto placement is using the container dimensions (if provided) or the element's parent to determine where to open the tooltip:
```javascript
var $container   = this.options.container ? $(this.options.container) : this.$element.parent()
var containerDim = this.getPosition($container)
```
This is quite broken in fact, because the parent element could be just a small div outside the element for example, leading in a totally random placement (placing the tooltip on top even if there's no room). And the container can also be outside of the viewport.

This fix simply uses the viewport instead, that's the purpose of the viewport actually, to position the tooltip.
So the auto placement should use it to find where there's more room.
By default this is body, which is good.

Closes #16073 by merging it

To ensure that we don't accidentally use any of the aliases.
This should prevent any future regressions from #12761.
Also updates the test suite since it now can't use these aliases either.

X-Ref: #15953
Closes #15952 by merging a tweaked version of it.
[skip sauce]
[skip validator]

Appears to be unnecessary and is broken by #16011,
which is otherwise quite sane.

Thanks to @peterblazejewicz & @Nikita240
Adds unit tests based on #14417
X-Ref: #14282
Closes #15807

Erratum from #15496

[Fixes #15953] Implement `assert.expect` in each unit test

Fixes #15136.
Closes #15345.
Closes #15314.
Refs #14724, #14927.

When the first two elements in a scrollspy content block have a document
offset of zero (i.e. they're hard against the top of the page),
Scrollspy would switch between them on every scroll event.

This could happen, for example, in a system of nested sections:

```
<section id="animals">
  <section id="dogs">
	Content
  </section>
</section>
```

This ocurred because Scrollspy's check to see if it's at the end of the
array of sections uses `!arr[index]`. This misses the case where
`arr[index]` does exist and is zero.

This commit explicitly checks the array bounds.

Since only on iOS tests fail when the fixture is displayed off-screen, see https://travis-ci.org/twbs/bootstrap/jobs/52605742

Fixes #15741
Closes #15751 by merging it.

Refs http://qunitjs.com/upgrade-guide-2.x/#replace-qunit-jsdump-with-qunit-dump

Refs http://qunitjs.com/upgrade-guide-2.x/#replace-qunit-log-callback-with-qunit-log-callback-for-all-reporting-callbacks