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Now CreationException contains a list of instances, and Creator manages its current list always up to date, passing it to the exception when needed.
The Exception will make a copy of the list to prevent external changes to it.
Added more tests.
Added pre- and post-instantiation listeners.
To make the Creator class more readable, delegated the task of managing the listeners to a new class, CreatorListenersManager.
Added tests to check the new functionality.
Resolved more conflicts in the tests.