data-quality-testinglisted

# Data Quality Testing ## Test like code not_null / unique / accepted_values / relationships on the columns that matter; **build fails** on violation. Untested transforms = silent downstream corruption. ## Freshness Assert source freshness; **stop** rather than serve stale marts as fresh. ## Contracts Model contracts (names/types/constraints) on consumer-facing models so upstream changes can't silently break a dashboard. ## Beyond schema Singular tests for business invariants (line items sum to order total). **Anomaly detection** (row-count drop, distribution shift) catches what schema tests miss -> significance to `applied-statistics`.