Content is rendered into wrong element in tests

[dagroe]

In testing environment the content of dropdowns is rendered into config['APP']?.rootElement (which is ENV.APP.rootElement = '#ember-testing'; by default) instead of the defined destination or the default ember-basic-dropdown-wormhole.

In our acceptance tests this leads to wrongly placed content in tests. Should config['APP']?.rootElement be considered a fallback if neither destination nor ember-basic-dropdown-wormhole are available?

[mkszepp]

@dagroe thanks for reporting. I thinks its possible to change... Would you like to make a PR for this?