The ValidateDocumentList() function used in controller_test.cpp unit tests requires that the sequence of FTDC records read from the file completely match the expected test vector input. With the introduction of periodic metadata sampling records (PM-3290) which can be interleaved with metric chunk records, figuring out the exact sequence of FTDC records that are expected to be written becomes much less straightforward. There should be another way to validate the sequence of FTDC records by category.