Definition
An alteration to the structure of a database table — adding or removing a column, changing a data type, modifying whether a column allows null values, or altering an index or constraint. Schema changes are one of the most common causes of production incidents, often because they happen silently through migrations or ORM updates without the full team noticing.
Why it matters
Schema changes are invisible to CI. Your code tests pass because the code is correct — but if a column was removed or a type changed in production that your application code still expects, nothing in CI will catch it. The first time you find out is when customers report errors.
How Well Tested handles it
Well Tested tracks schema changes detected in your release pipeline, correlating them with historical incidents to surface patterns like 'this column has caused billing incidents 3 times in the last 90 days.' At release time, Well Tested checks whether any schema changes in the diff could break downstream systems.
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