app.test.tsx changes

[mbondyra]

Summary

Summarize your PR. If it involves visual changes include a screenshot or gif.

Checklist

Delete any items that are not applicable to this PR.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• This was checked for keyboard-only and screenreader accessibility
• This renders correctly on smaller devices using a responsive layout. (You can test this in your browser
• This was checked for cross-browser compatibility, including a check against IE11

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[dej611]

Tested locally and works great.
Noticed the Provider error messages but I think we can work around those later on.

[dej611]

One question here.
What's the benefit of having a shared variable and reset it on every test with a beforeEach vs generating all the mocks explicitly every time?
It is just code readability (not calling it every time) or there's more?

[dej611]

In the original code there's a cloneDeep function that wraps this to enable document manipulation within tests without worry about influencing other tests.