Apply when you write, change, or keep a test. Assert what the code's users can observe, so that the test fails when that behavior breaks and keeps passing when only the internals change.
The English summary is being prepared. Showing the original description.
See how to installReview the instructions the agent will receive before you install.
A test is a claim about what the code does for its users: a caller, an end user, or another service. Behavior is what those users can observe through the interface they use. That includes return values, errors, state they can read back, and effects on systems outside the code, such as a request sent, a row written, or a message emitted. Implementation is what they cannot observe: private helpers, internal call order, intermediate data, and which internal collaborator did the work.
Judge each test against two imagined edits:
Keep a test that catches the first edit and survives the second. Rewrite or delete the rest. To write a test that does both, drive the code through its users' interface with a concrete input. Derive the expected value from the requirement, not from a run of the code. Assert what the contract promises, no less and no more.
The contract decides, not the shape of the assertion. When "an empty cart never charges" is the promise, an assertion that the payment client got no call is behavior. Pair it with a case where the charge happens, so that the test shows it can see a call. The payload that a mocked external service receives is behavior, because that service observes it. A call to an internal helper is implementation, because no user can see it. An empty list is the exact answer when no record matches, and a hollow check when the test only needs some result. An exact error message pins wording that no caller reads. The error type that callers branch on is the contract.
A test can pin an invariant instead of a call, such as a key that must exist in two tables or a compile-time type check. The invariant is the behavior.
No reviews yet. Tell others what you thought.
No login needed. Share how it worked for you, ask a question, or note where it did not run.
No comments yet. Be the first to write one.
Sketch types, signatures, and module structure before code, then stay in the loop while implementation fills in. Use for /architect, 'architect this', 'design this', or non-trivial work where jumping to code would lock in the wrong shape.
The English summary is being prepared. Showing the original description.
Spawn N parallel candidates at the same task, pick a base, graft the strongest parts of the losers into it. Use for /arena, 'arena this', 'throw it in the arena', or when one attempt at a non-trivial artifact would lock in the wrong shape.
The English summary is being prepared. Showing the original description.
Use for "automate me", "create/update/refresh my -mode skill", "turn/capture my preferences or working style into a skill", or wanting agents to follow how the user works. Drafts or revises a personal -mode skill via create-skill + unslop, optionally pulling fresh evidence from recent transcripts.
The English summary is being prepared. Showing the original description.
Vet a perf measurement (limiter, tuning, limits, errors, repeatability, relevance, and whether the work happened) before you report or act on it. Use when you run a benchmark or report a speedup or regression you measured.
The English summary is being prepared. Showing the original description.
Find what a change could break somewhere else before it ships, beyond the diff, and prove the one fact it's safe because of by running real code instead of writing it up. Use for 'blast radius of X', 'what could this break', or reviewing a small diff you don't trust.
The English summary is being prepared. Showing the original description.
Restate the last message in plain human language, with no jargon.
The English summary is being prepared. Showing the original description.