test-debugger

test-debugger is a skill for Claude Code, Codex from lfyxhappy/lfcode. It costs 54 tokens per session (345 once invoked), scanned A, original, MIT.

A test-failure diagnosis guide for tests that fail, hang, or produce unexpected results. It reproduces the narrowest failure and separates a faulty test from a product bug or an environment problem.

In plain words
What is it for?
Use it to investigate assertion mismatches, fixture problems, timing issues, resource leaks, dependency mismatches, and tooling failures. When authorised, it can make the smallest fix and rerun focused checks.
Why use it?
It prevents teams from hiding failures by weakening assertions, adding arbitrary delays, or skipping tests. It bases the diagnosis on actual commands, inputs, outputs, logs, cleanup, and recent changes.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to investigate assertion mismatches, fixture problems, timing issues, resource leaks, dependency mismatches, and tooling failures. When authorised, it can make the smallest fix and rerun focused checks.

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Install with agentmods
npx agentmods add skills/lfyxhappy/lfcode/test-debugger
Install

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.

Any agent
npx skills add lfyxhappy/lfcode --skill test-debugger
Clone the repo
git clone --depth 1 https://github.com/lfyxhappy/lfcode

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for test-debugger

README.md
[![agentmods](https://agentmods.dev/badge/skills/lfyxhappy/lfcode/test-debugger/github.svg)](https://agentmods.dev/skills/lfyxhappy/lfcode/test-debugger)
Your own site
<a href="https://agentmods.dev/skills/lfyxhappy/lfcode/test-debugger"><img src="https://agentmods.dev/badge/skills/lfyxhappy/lfcode/test-debugger/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.

agentmods 80×15 button for test-debugger

Your own site · 80×15
<a href="https://agentmods.dev/skills/lfyxhappy/lfcode/test-debugger"><img src="https://agentmods.dev/badge/skills/lfyxhappy/lfcode/test-debugger.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 345 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00054 $0.00345
Opus 5 $0.00027 $0.00172
Sonnet 5 $0.00011 $0.00069
Haiku 4.5 $0.00005 $0.00034

Measured 5d ago against content hash aa70ec3b56fa, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

test-debugger 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 5d 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.

packages/lfcode/src/skill/lfcode/.bundle/test-debugger/SKILL.md · 28 lines

What it actually says

Test Debugger

Diagnose failures from reproducible evidence and keep test intent intact.

Workflow

  1. Read repository instructions, package scripts, the failing test, its fixture setup, and recent relevant diffs.
  2. Record the exact package, command, runtime, and failure output. Run the smallest reproducible test first, then repeat only when checking flakiness.
  3. Classify the failure as assertion mismatch, setup/fixture problem, timing or concurrency issue, resource leak, dependency mismatch, or environment/tooling failure.
  4. Trace the failing code path and inspect actual inputs, outputs, logs, and cleanup. Do not guess from a stack frame alone.
  5. If a change is requested, make the smallest fix that preserves the test's behavioral contract. Add a regression case only when it captures a missing contract.
  6. Rerun the focused test, then the affected package checks when shared code or interfaces changed.

Boundaries

  • Do not delete, weaken, skip, broaden, or rewrite a failing assertion merely to obtain a green run.
  • Separate a diagnosis, a recommended fix, and an implemented fix in the report.
  • Avoid flaky sleeps and mocks that hide the real failure. Redact secrets and machine-specific data from logs.

Completion check

Report the reproduction command, root cause or bounded hypothesis, changed files if any, and every verification command that passed or remains unavailable.

Changes

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.

  1. 5d ago First seen · 28 lines · 54 tokens per session scan A aa70ec3b56fa

Subscribe to this mod's changes

test-debugger is a skill published in the GitHub repository lfyxhappy/lfcode (2 stars, last pushed 8d ago), licensed MIT. It adds 54 tokens to every session and 345 once invoked, about $0.0003 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 2026-09-05.