Definition
Comparing the structure or content of a database table between two points in time — typically between a staging environment and production, or between before and after a release. A table diff checks schema (columns, types, constraints) and optionally data (row counts, aggregate values, keyed unmatched rows).
Why it matters
Table diffs catch changes that code review misses. A column added in a migration looks fine in isolation — but if your billing service reads that column as a string and the migration changed it to a timestamp, production breaks silently. Table diffs catch this before customers do.
How Well Tested handles it
Well Tested runs table diffs as part of the release check, comparing production state against the expected post-release state. It checks schema integrity (column presence, types, nullability), row count variance, keyed unmatched rows, and critical schema counts. Results feed into the release risk score.
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