Unit test for pull request #24240

Use a virtual scrollbar as this is simpler than having a real one (overflow: scroll doesn't seem to work in Phantom), and disable it for the new test.

One test has also been altered to prevent erroneous fails when other inline styles are added to the body (e.g. overflow).

When the body does not overflow (achieved by hiding the QUnit container), it should not be given a margin.

* Adjust margin for sticky elements on modal

Previously white space was visible to the right of sticky elements due to right padding being added to the body. This fixes #23661.

* Add unit tests for margin of sticky elements on modal

Fixes #19878

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add modal my gawd

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.

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

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

Refs #15893

Add tests for `aria-hidden` of modal

Use strictEqual of 1 here instead of 2 asserts

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