This represents failure information for the test runner. It encapsulates multiple sets
of exceptions so that it can provide inner exception information, including support for
AggregateException. The parent indices indicate the hierarchy of the exceptions
as extracted during the failure; the 0th exception is always the single parent of the tree,
and will have an index of -1.
The parent exception index for the exceptions; a -1 indicates that
the exception in question has no parent.