| name | test-regression-design |
| description | Design or update regression coverage for autodarts-xconfig. Use when a bug fix, feature change, or refactor needs tests at the domain, runtime, config, or DOM harness layer. Do not use for release-only work or README-only edits. |
Goal
Design tests that lock in intended behavior and prevent repeated regressions.
Guardrails
- tests should describe behavior, not implementation trivia
- choose the narrowest effective layer that proves the contract
- include at least one test that reproduces the old bug or a close equivalent
Workflow
1. Identify the regression class
Classify the failure as:
- semantic or domain error
- runtime mapping or lifecycle error
- DOM shape or observer error
- config or defaults drift
- integration mismatch between modules
2. Pick the narrowest effective test layer
Prefer:
- domain tests for rules, normalization, ordering, ownership, perspective, and scoring
- runtime tests for snapshot mapping, lifecycle, rerender rules, and observer behavior
- harness tests for DOM shape, merged rows, node replacement, and mount churn
3. Capture the failure mode and edge conditions
Where useful, cover:
- noisy or partial input
- repeated rerenders
- swapped ownership or order
- unchanged semantic state with replaced DOM nodes
- alternate mode variants
- fallback behavior
Output requirements
A valid result from this skill must:
- add or update tests near the correct layer
- protect the changed behavior from regression
- use names that explain the behavioral contract
- avoid shallow tests that only restate the code
