The files in unit_test are the full set of fields and fields used for the unit tests.
These files are used by the MET regression tests that are run locally.

The files in vX.Y/unit_test (where vX.Y is the latest version available in this directory) are paired down from the full set.
These files are used by the MET unit tests that are run in GitHub Actions.
Some files are modified to create a subset of the fields, e.g. using wgrib2 to remove fields.
Some files may be excluded from this version, e.g. climatology files that are not used in the MET unit tests.