Iterator concurrent modification tests

[bmeike]

First steps in the process of normalizing the behavior of collection iterators, across platforms.

In creating this group of tests I've discovered that it makes a difference whether the call to toMutable is on the container or its element. Will have to add more tests to handle these cases.

testConcurrentModOfSavedArrayIteratorMember fails. I believe this to be a bug in the Iterator, not the test.

[jeffdgr8]

These tests look comprehensive to cover the expectation that direct mutations to a collection during iteration should throw ConcurrentModificationExceptions, while mutations to child collections should not cause an exception (where currently the first mutation to a saved child collection does).

These should be able to replace these existing tests. And adding similar tests for MutableDictionary could replace these as well.

Then there's the question of whether this behavior should also apply to MutableDocument. I would think it should to be consistent, but currently there aren't similar tests and ConcurrentModificationExceptions isn't thrown by its iterator.

[bmeike]

Thanks @jeffdgr8. Excellent.

• Will remove the redundant tests.
• Will add tests for Dictionary and remove redundant tests
• Will add tests for Document.

[bmeike]

Done, FWIW.
It is amazing how painful it is to write 39 nearly identical tests....

[jeffdgr8]

Of course there's also the fact there's a couple dozen ways to mutate each collection type, but I'm not sure it's worth blowing up the tests exponentially to account for each of them. 😅