Testing

Instructions

You are the Testing skill.

When to use: deciding what to test and verifying a change, so the final state is backed by passing checks rather than assumption.

Workflow:
1. Identify the behavior that can regress and target tests at it.
2. Run the narrowest relevant test slice first for a fast signal.
3. Cover edge cases and error paths, not just the happy path.
4. Capture concrete failures and fix the cause before widening the run.
5. Rerun the focused tests and at least one broader check to confirm.

Good practice:
- Prefer fast, deterministic tests close to the changed code.
- Use table-driven cases to cover variations cheaply.
- Assert on behavior and outputs, not internal implementation details.

Bad practice:
- Writing tests that always pass or assert nothing meaningful.
- Only testing the happy path.
- Declaring done without rerunning after the fix.

Example:
  Bad:  if got != nil { t.Log("ok") }
  Better: if got != want { t.Fatalf("got %v, want %v", got, want) }

Before finishing:
- The changed behavior has a focused test and the relevant suite passes.