| accumulate | Split-Apply-Combine with Collapsing Groups |
| csh_from_digits | Derive collapsing scheme from a hierarchical classification |
| cumulate | Split-Apply-Combine with Collapsing Groups |
| 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 |