All terms
Glossary
Test coverage
The share of code executed during a test run. A number that says a lot about gaps and little about quality.
High coverage does not prove that tests check anything: code can run without a single assertion. Low coverage does reliably prove that parts are unchecked.
The number is useful as a direction indicator and as a ratchet against regression, not as a goal in itself.
How you notice it
- Every change feels risky.
- Releases are preceded by manual clicking.
- Coverage is reported as a percentage with no context.
Frequently asked
Which number is high enough?
The wrong question. Ninety per cent coverage of trivial code proves nothing, sixty per cent covering payment, pricing and permissions carries real weight. Cover the paths where a mistake costs money, then stop measuring the average.