What is test-coverage-gap-finder?

A review guide for finding important missing tests in .NET projects. It examines code and optional coverage reports, which show how much code tests exercise.

Use it to identify untested public types, skipped if/else or switch paths, and risky payment, authentication, calculation, or state-changing code.

A high overall coverage percentage can still leave critical code or branches untested, so it ranks gaps by risk instead of counting coverage alone.

test-coverage-gap-finder — Skill for Claude Code by StefanTheCode

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 StefanTheCode/dotnet-ai-toolkit --skill test-coverage-gap-finder

Clone the repo

git clone --depth 1 https://github.com/StefanTheCode/dotnet-ai-toolkit

Made for: Claude Code.

Or install dotnet-ai-toolkit, the plugin that ships this one along with the rest of its 49 skills.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/stefanthecode/dotnet-ai-toolkit/test-coverage-gap-finder/github.svg)](https://agentmods.dev/skills/stefanthecode/dotnet-ai-toolkit/test-coverage-gap-finder)

Your own site

<a href="https://agentmods.dev/skills/stefanthecode/dotnet-ai-toolkit/test-coverage-gap-finder"><img src="https://agentmods.dev/badge/skills/stefanthecode/dotnet-ai-toolkit/test-coverage-gap-finder/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/stefanthecode/dotnet-ai-toolkit/test-coverage-gap-finder"><img src="https://agentmods.dev/badge/skills/stefanthecode/dotnet-ai-toolkit/test-coverage-gap-finder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 104 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 618 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.

Model	Per session	Once invoked
Fable 5.1	$0.00104	$0.00618
Opus 5.5	$0.00042	$0.00247
Sonnet 5.5	$0.00021	$0.00124
Haiku 4.5	$0.00010	$0.00062

Measured 2mo ago against content hash 3afbd774bcd9, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

test-coverage-gap-finder 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 2mo 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.

skills/test-coverage-gap-finder/SKILL.md · 45 lines

What it actually says

Test Coverage Gap Finder

Find where tests are actually missing and prioritize by risk — so effort goes to the code that matters, not chasing a coverage percentage.

Input — point it at your project / coverage report

Works on a target: a project or GitHub URL, and optionally a coverage report (coverage.cobertura.xml, lcov). Map code vs tests:

grep -rln "public class\|public record" --include=*.cs <target> | grep -vi "Tests"
find <target> -iname "*Tests.cs" -o -iname "*.Tests.csproj"
# if a coverage file exists, parse it for low/zero-covered members

Generate coverage if asked: dotnet test --collect:"XPlat Code Coverage".

How it prioritizes (risk, not vanity %)

Untested public types with real logic — services, handlers, domain methods, validators. High priority.
Uncovered branches in covered classes — the if/else/switch arms tests skip (where bugs hide).
Complex/critical code — payment, auth, calculations, state transitions — weighted up even if partly covered.
Deprioritize — DTOs/POCOs, generated code, trivial getters: low value to test.

Output

## Coverage gaps (ranked)
🔴 <Type> — no tests; contains <business logic> → suggest: <key cases>
🟡 <Type.Method> — branch `<condition>` uncovered → add case
🟢 (skip) <DTOs / generated / trivial>
## Suggested next 5 tests
1. ...  (hand off to xunit-test-generator)

Principles

Coverage % is a vanity metric. 100% of trivial code is worthless; 60% covering all the risky branches is great.
Prioritize by risk × complexity, not line count.
A gap in a payment/auth path outranks ten gaps in DTOs.
Don't recommend tests for code that can't meaningfully fail.

How to use it & best prompts

"What's not tested in this project", "where should I add tests next", "analyze my coverage report and prioritize", "find untested business logic". Hands off to xunit-test-generator and test-data-builder-generator.

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.

USAGE.md 874 B

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.

2mo ago First seen · 45 lines · 104 tokens per session scan A 3afbd774bcd9

Subscribe to this mod's changes

test-coverage-gap-finder is a skill published in the GitHub repository StefanTheCode/dotnet-ai-toolkit (26 stars, last pushed 2mo ago), licensed MIT. It adds 104 tokens to every session and 618 once invoked, about $0.0004 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 2026-08-30.

Testing Unit testing

test-coverage-gap-finder next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
test-coverage-gap-finderStefanTheCode/dotnet-ai-toolkit	Skill	26	2mo ago	MIT	A	104	Claude Code
test-masterJeffallan/claude-skills	Skill	12k	7d ago	MIT	A	104	Claude Code
migrate-xunit-to-xunit-v3dotnet/skills	Skill	5.8k	yesterday	MIT	A	149	Claude Code
go-testingGentleman-Programming/gentle-ai	Skill	8.4k	yesterday	MIT	A	26	Claude Code, Codex
principle-test-behavior-not-implementationmichael-denyer/pstack-claude	Skill	4.1k	yesterday	MIT	A	50	Claude Code
dart-testdartsim/dart	Skill	1.2k	yesterday	BSD-2-Clause	A	18	Claude Code, Codex
test-generatorrshankras/claude-code-apple-skills	Skill	864	2d ago	MIT	A	33	Claude Code