testing-changes — Claude Code skill: what it does, how to install
Defines test requirements for code changes, enforcing regression tests for bug fixes, edge-case coverage, and strict checks against empty test diffs.
npx skills add riekelt/principal-engineer --skill testing-changes -a claude-codeWhat testing-changes does
This skill determines what tests a pull request owes whenever software behavior changes. If a pull request modifies system logic without updating test files, the skill treats the empty test diff as a review defect. Bug fixes must come with a regression test showing a failure on the unfixed code before turning green. Tests must isolate the defect.
Happy paths alone are not enough. The skill directs agents to cover failure branches and surfaced edge cases, requiring a targeted verify command for each task. Silencing failing checks by skipping or weakening assertions is forbidden. When an assertion breaks, authors must fix the root cause instead of ignoring it.
You need the principal-engineering skill installed beforehand as required background. Without it, the agent cannot map invariants or risk tiers to project critical paths. The skill does not mandate strict test-first workflows, leaving the creation order to developer preference.
What it helps with
- review whether a pull request includes sufficient tests for behavior changes
- write a reproducible regression test that fails before a bug fix is applied
- define an isolated verification command for a targeted task
- verify invariants and reconciliation logic on critical data paths
Example prompts for the agent
- Review this diff and tell me what tests are missing for the behavior changes
- Draft a regression test for the checkout failure that fails on the unfixed code
- What test coverage does this refactoring task owe before merging?
How to install testing-changes
1Skills CLI (Vercel)
npx skills add riekelt/principal-engineer --skill testing-changes -a claude-code2Manually: put the files in place
~/.claude/skills/testing-changes/SKILL.mdCopy the whole skill folder; for one project use .claude/skills/testing-changes/
1Skills CLI (Vercel)
npx skills add riekelt/principal-engineer --skill testing-changes -a codex2Manually: put the files in place
.agents/skills/testing-changes/SKILL.mdFor all projects use ~/.agents/skills/
1Skills CLI (Vercel)
npx skills add riekelt/principal-engineer --skill testing-changes -a cursor2Manually: put the files in place
.cursor/skills/testing-changes/SKILL.mdCursor also reads .agents/skills/ and .claude/skills/
1GitHub CLI
gh skill install riekelt/principal-engineer testing-changes2Manually: put the files in place
.github/skills/testing-changes/SKILL.md1Skills CLI (Vercel)
npx skills add riekelt/principal-engineer --skill testing-changes -a gemini-cli2Platform CLI
gemini skills install https://github.com/riekelt/principal-engineer --path plugins/principal-engineer/skills/testing-changesManually: put the files in place
.devin/skills/testing-changes/SKILL.mdThe legacy .windsurf/skills/ path still works
Skills CLI (Vercel)
npx skills add riekelt/principal-engineer --skill testing-changes -a opencodeClaude.ai
Zip the folder and upload it in Settings → Capabilities → Skills
Step by step, with commands for each platform: How to install skills in Claude Code: five ways
Questions about testing-changes
How to install testing-changes in Claude Code?
Run npx skills add riekelt/principal-engineer --skill testing-changes -a claude-code.
Does testing-changes require a test-driven development workflow?
No. The skill governs what tests must exist when a change lands, but it does not dictate whether tests are written before or after implementation code.
What prerequisites are required for this skill?
It requires the principal-engineering skill as a background dependency to understand risk tiers and critical path invariants.
