Which edge cases and tests matter most?
Understand the concept
Edge cases are valid boundary conditions and failure situations that ordinary examples may not exercise. Useful tests prove important rules under those conditions, including concurrent and repeated requests. The highest-value case is often where a missing record, denied access or partial failure changes control flow.
Important ideas
-
Missing records, invalid input, denied access and duplicate requests.
-
Concurrent updates, transaction rollback and dependency failures.
-
Test final behavior and database rules, not just whether a mocked method was called.
-
Test the database-backed invariant when the bug depends on concurrency; two mocked calls cannot prove a unique constraint works.
Can you explain it without the notes?
Which edge cases and tests matter most?
Use your own words. Explain an example and one limitation before checking the explanation.
Check your explanation
Edge cases are valid boundary conditions and failure situations that ordinary examples may not exercise. Useful tests prove important rules under those conditions, including concurrent and repeated requests. The highest-value case is often where a missing record, denied access or partial failure changes control flow.
Turn this concept into a clear answer.
- Connect each requested test to a real failure it would catch.
Keep connecting the ideas.
Next lesson: What can break in production, and how would I debug it?Adapted from 11_AI_CODE_REVIEW.md · “Which edge cases and tests matter most?”. Examples are study fragments; framework behavior can depend on your version.