Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add dayfinggg/openai-codex-agent-skills --skill tddgit clone --depth 1 https://github.com/dayfinggg/openai-codex-agent-skillsWrote 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/dayfinggg/openai-codex-agent-skills/tdd)<a href="https://agentmods.dev/skills/dayfinggg/openai-codex-agent-skills/tdd"><img src="https://agentmods.dev/badge/skills/dayfinggg/openai-codex-agent-skills/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/dayfinggg/openai-codex-agent-skills/tdd"><img src="https://agentmods.dev/badge/skills/dayfinggg/openai-codex-agent-skills/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 | $0.00022 | $0.00779 |
| Opus 5.5 | $0.00009 | $0.00312 |
| Sonnet 5.5 | $0.00004 | $0.00156 |
| Haiku 4.5 | $0.00002 | $0.00078 |
Grade A, and why
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 today.
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.
How it starts
The opening of the file, as written. The whole thing — 41 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Read local host integration before applying this imported workflow.
Test-Driven Development
TDD is the red → green loop. This skill is the reference that makes that loop produce tests worth keeping: what a good test is, where tests go, the anti-patterns, and the rules of the loop. Every section applies on every cycle: consult them before and during the loop, not after.
When exploring the codebase, read GLOSSARY.md (if it exists) so test names and interface vocabulary match the project's domain language, and respect ADRs in the area you're touching.
What a good test is
Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't. A good test reads like a specification: "user can checkout with valid cart" tells you exactly what capability exists, and it survives refactors because it doesn't care about internal structure.
See tests.md for examples and mocking.md for mocking guidelines.
Seams: where tests go
A seam is the public boundary you test at: the interface where you observe behavior without reaching inside. Tests live at seams, never against internals.
Select observable test seams from the requested behavior, public contract, and existing tests. Reuse scope already established in the conversation. Concentrate effort on critical paths and complex logic. Do not require a new user confirmation for routine test-boundary choices within the authorized task.
Identify the public interface and what each chosen seam can and cannot observe. Inspect callers and tests before asking. Ask only if an unresolved interface decision materially changes the requested behavior.
When the shape of that interface is itself in question (how deep the module is, where the seam belongs, what the interface should expose), read the installed codebase-design skill using the host's available skill or file-reading capability for the vocabulary. It is the shared source of the module, interface, depth, seam, adapter, leverage and locality terms, and it is a reference to consult, not a session to run.
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- today Changed · +10 lines · -16 tokens per session 8fc3659a8155
- 1mo ago Changed · +3 tokens per session 95478e0ff7b8
- 1mo ago Changed · -2 lines · -33 tokens per session e90ee8eb6abb
- 1mo ago Changed · +2 lines 749cc5824d08
- 1mo ago Changed · +2 lines c770104e9ce7
- 2mo ago First seen · 29 lines · 68 tokens per session scan A 20f2bfeb5376
tdd is a skill published in the GitHub repository dayfinggg/openai-codex-agent-skills (8 stars, last pushed today), licensed MIT. It adds 22 tokens to every session and 779 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-08-31.
Other skills, from other repositories
test-driven-development
Use when implementing any feature or bugfix, before writing implementation code. Enforces red-green-refactor cycle with strict rules.
tdd-workflow
A test-first development workflow, commonly called TDD, where a failing test is written before the code that should make it pass. The cycle then adds the smallest working change and cleans it up.
test-writer
Write thorough tests following TDD and BDD principles.
programming
USE FOR: Programming/debugging: Bash, Python/Jupyter quality, Nix package workflow, Terraform with Checkov, Markdown, TDD/Tidy First, and root-cause isolation. DO NOT USE FOR: agent harness, data-platform, diagramming, or GitHub workflow work.
debug
Debug a stubborn bug with a deterministic reproduction, hypothesis ledger, one-variable fixes, and a regression test. Use after the first obvious look fails, reproduction is unclear, or a fix attempt failed. Not for routine obvious failures; use for "ไล่บั๊ก".
tdd
Canon test-driven development (specify, encode, fulfill) for the host project's test framework. Clarify specifications, one failing test at a time, minimal code to green, approval gates, kitchen-cleaning refactor when needed. Use for TDD, specify-encode-fulfill, or red-green-refactor sessions.