[COLLECTIONS-898] AbstractSetTest cannot be used with an explicitly typed Set (unless it's based on String)

[tmortagne]

Pick a valid element from getFullElements(), instead of adding a hardcoded String.

I did not dare making more changes to the logic of that test, but I'm honestly not sure there is that much value in the "Empty set shouldn't equal nonempty set" bit, compared to the "Sets with different contents shouldn't be equal" one at the end. I mean it's not really the point of this test to validate the #add vs #addAll APIs behaviors.

There does not seem to already exist a test class designed specifically to validate AbstractSetTest behavior (but there are various test classes which rely on AbstractSetTest), so I did not create a new one for such a small change. But I may have missed it.

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[garydgregory]

Jira ticket is COLLECTIONS-898.

[tmortagne]

Hmm, indeed sorry about that bad copy/paste. Fixed.

[garydgregory]

@tmortagne Thank you, merged 🚀

[tmortagne]

Thanks !