test-coverage

A patch-focused test check that runs tests only in packages changed by the current branch and checks coverage for newly added lines.

In plain words
What is it for?
Use it to check whether a patch's tests pass and whether its added code has meaningful test coverage.
Why use it?
It avoids waiting for the full test suite while still finding failures in affected packages and missing tests for new code.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/cloudposse/atmos/test-coverage
Any agent
npx skills add cloudposse/atmos --skill test-coverage
Clone the repo
git clone --depth 1 https://github.com/cloudposse/atmos

Made for: Claude Code, Codex.

Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,619 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00076 $0.01619
Opus 5 $0.00038 $0.00809
Sonnet 5 $0.00015 $0.00324
Haiku 4.5 $0.00008 $0.00162

Measured 2d ago against content hash 14e8b89eb580, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

test-coverage 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 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/patch-test-coverage.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

.claude/skills/test-coverage/SKILL.md · 114 lines

How it starts

The opening of the file, as written. The whole thing — 114 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test Coverage (patch-scoped)

Answers two questions about the current branch's patch vs origin/main: are its tests passing, and is it adequately covered? Both come from the same scoped test run, so one skill owns both.

Why patch-scoped, not full-suite

The full suite is 349 packages / 1876 test files and takes 45-75 minutes per CI timeouts — running it every hour is not feasible. This skill only ever runs tests for packages containing files this patch touched — it never expands to the other 340+ packages just to go looking for trouble. But once a package is in scope and its run turns up a failure, fix it regardless of whether that specific test or file is what this patch changed: what this loop cares about is the packages it touched actually passing, not whose commit originally broke them.

Running the check

atmos fix coverage [base-ref]

(atmos fix tests [base-ref] is an equivalent alias — same underlying run, reach for it when the question framing is "are my tests passing" rather than "is my patch covered.") Defaults to origin/main. This wraps .claude/skills/test-coverage/scripts/patch-test-coverage.sh, which deliberately does no line-level analysis itself — it just prints a raw bundle (pass/fail status, raw test output if failed, the coverage profile if passed, and the diff) for the fixing agent to reason over directly, the same way coderabbit-review reads raw CodeRabbit markdown rather than us pre-parsing it.

Three outcomes:

  • STATUS: NO_GO_CHANGES — no touched .go files. One-line no-op, done.
  • STATUS: TESTS_FAILING — go to "Fix failing tests" below.
  • STATUS: OK — tests pass; go to "Fix coverage gaps" below.

Fix failing tests (gates coverage — a package with failing tests has meaningless coverage

numbers)

Delegate to Agent subagent_type: "test-coverage-fix", Section A, passing the raw failing-test output and the list of touched files. The agent classifies each failure as in-scope (the file lives among this patch's touched files) or pre-existing (it doesn't), but scope only changes how much diagnosis a fix needs — not whether an attempt is made. What this loop cares about is the suite passing, full stop; "not this patch's fault" is not a reason to leave something red. Confirmed for real: a "pre-existing failure" was itself a false positive in the check, not the code — the patch-scoped go test run had no -timeout override, so Go's 10-minute binary default tripped on the full (patch-unrelated) ./tests acceptance package under load, panicking on whichever subtest happened to still be running when the clock ran out. The fix was to the test-infrastructure itself (patch-test-coverage.sh now passes -timeout 40m, matching .atmos.d/test.yaml's full-suite convention) — exactly the kind of pre-existing-but-fixable root cause this agent should resolve rather than just report.

Read the full file on GitHub · 114 lines

Files

What ships with it

1 file 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.

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. 2d ago First seen · 114 lines · 76 tokens per session scan A 14e8b89eb580

Subscribe to this mod's changes

test-coverage is a skill published in the GitHub repository cloudposse/atmos (1,367 stars, last pushed today), licensed Apache-2.0. It adds 76 tokens to every session and 1,619 once invoked, about $0.0004 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.