accumulate              Split-Apply-Combine with Collapsing Groups
csh_from_digits         Derive collapsing scheme from a hierarchical
                        classification
frac_complete           Demand minimal fraction of complete records
from_validator          Use a validate::validator object to define a
                        test
min_complete            Demand minimal number of complete records
min_records             Demand minimal number of records
producers               Synthetic data on producers
smoke_test              Check your testing function against common edge
                        cases
