Daily feed is a file of approx 60,000 lines.
This contains self-referential lookups, lookups
into 1/2 a dozen varying VSAM tables,
lookups into our daily changing BOM master,
lookups into our daily changing inventory,
with multiple stopping points as people scramble
to modify one of those files when they find
a lookup doesn't match, either overriding the
lookup with a hack of the data, or overriding
to point to a different entry in one of
our files, or a combination.

Every single one of these files must match
for a successful run, and they are never the
same from day to day. No way in hell to pull
any historical data more than 7 days old, which
means a miniscule amount of code can be tested
since the input is wildly varying based on the
campaign of the moment.