Borrowing it
Nothing to install: this file belongs to JubaKitiashvili/everything-react-native-expo. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/JubaKitiashvili/everything-react-native-expo/main/.claude/skills/erne-tdd/SKILL.mdgit clone --depth 1 https://github.com/JubaKitiashvili/everything-react-native-expoWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/jubakitiashvili/everything-react-native-expo/erne-tdd)<a href="https://agentmods.dev/skills/jubakitiashvili/everything-react-native-expo/erne-tdd"><img src="https://agentmods.dev/badge/skills/jubakitiashvili/everything-react-native-expo/erne-tdd/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/jubakitiashvili/everything-react-native-expo/erne-tdd"><img src="https://agentmods.dev/badge/skills/jubakitiashvili/everything-react-native-expo/erne-tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00018 | $0.00400 |
| Opus 5 | $0.00009 | $0.00200 |
| Sonnet 5 | $0.00004 | $0.00080 |
| Haiku 4.5 | $0.00002 | $0.00040 |
Grade A, and why
erne-tdd scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
/erne-tdd — Test-Driven Development
You are executing the /erne-tdd command. Use the tdd-guide agent to implement features test-first.
Red-Green-Refactor Cycle
1. RED — Write Failing Test First
// Write the test BEFORE any implementation
test('LoginButton shows loading state during auth', () => {
render(<LoginButton onPress={mockAuth} />);
fireEvent.press(screen.getByRole('button', { name: 'Log In' }));
expect(screen.getByTestId('loading-spinner')).toBeVisible();
});
Run the test — confirm it FAILS (red).
2. GREEN — Write Minimum Code to Pass
Implement only enough code to make the test pass. Do not over-engineer.
3. REFACTOR — Clean Up
Improve code quality while keeping tests green:
- Extract shared logic into hooks
- Improve naming and readability
- Remove duplication
Testing Stack
- Unit/Component: Jest + React Native Testing Library
- E2E: Detox (when needed for user flows)
Workflow
- User describes the feature to implement
- Write test(s) for the first behavior
- Run test — verify it fails
- Implement minimum code
- Run test — verify it passes
- Refactor if needed
- Repeat for next behavior
- When feature is complete, run full test suite
Rules
- Never write implementation code without a failing test first
- Test behavior, not implementation details
- Query elements by role, text, or label (not testID unless necessary)
- Mock at boundaries (API, native modules), not internals
- Reference
rules/common/testing.mdfor conventions
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 11d ago First seen · 52 lines · 18 tokens per session scan A c0dfdcfee72e
erne-tdd is a skill published in the GitHub repository JubaKitiashvili/everything-react-native-expo (45 stars, last pushed 5mo ago), licensed MIT. It adds 18 tokens to every session and 400 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
engram-testing-coverage
TDD and coverage standards for Engram. Trigger: When implementing behavior changes in any package.
iterative-development
TDD iteration loops using Claude Code Stop hooks - runs tests after each response, feeds failures back automatically.
python
Python development with ruff, mypy, pytest - TDD and type safety.
nw-fp-clojure
Clojure language-specific patterns, data-first modeling, REPL-driven development, and spec.
strict-tdd
Strict RED->GREEN->REFACTOR test-driven development with enforcement. Never write production code before a failing test. Atomic commits per TDD cycle.
mobiai-mobile-tdd
You MUST use this before writing any implementation code for a mobile feature, bug fix, refactor, or behavior change. Tests come before implementation — no exceptions.