Graph-informed mutation testing triage. Parses codebases with Trailmark, runs mutation testing and necessist, then uses survived mutants, unnecessary test statements, and call graph data to identify false positives, missing test coverage, and fuzzing targets.
SkillScore82Maintained
Automatic
◆QA & Test Engineering pack
Last verified 8/12/2026
What it changes
Passed 16 of 19 test cases with the skill, and 3 of 19 without it.
Without skill18%
With skill82%
Checks it passed that the model alone missed
Classifies the mutant as a false positive
Categorizes the finding as a fuzzing target
Classifies the finding as a corroborated finding
and 16 more in the full report
14 fixed4 passed either way4 still failing0 broke
Pass-rate lift
+64 pp
Tokens
+114%
Agent turns
0%
Response time
-50%
Model gemini-3.6-flashMeasured 8/12/2026v118 of 22 cases passed with skill · 19 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 14 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 14
Prompt
We are writing a Python script to automate graph analysis for mutation triage using QueryEngine. What mandatory API call must be executed on the engine object after loading from directory but before classifying findings?
What was checked, without and with the skill
Checked
Without skill
With skill
Calls engine preanalysis before triaging findings
Passed
Passed
Uses pre-analysis subgraphs to determine triage buckets
Missed
Passed
case-20 · gemini-3.6-flash · 8/12/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md334 lines5 files
Genotoxic
Combines mutation testing and necessist (test statement removal) with
code graph analysis to triage findings into actionable categories:
false positives, missing unit tests, and fuzzing targets.
When to Use
After mutation testing reveals survived mutants that need triage
Identifying where unit tests would have the highest impact
Finding functions that need fuzz harnesses instead of unit tests
Prioritizing test improvements using data flow context
Filtering out harmless mutants from actionable ones
Finding unnecessary test statements that indicate weak assertions (necessist)
When NOT to Use
Codebase has no existing test suite (write tests first)
Pure documentation or configuration changes
Single-file scripts with trivial logic
Prerequisites
trailmark installed — if uv run trailmark fails, run:
uv pip install trailmark
DO NOT fall back to "manual verification" or "manual analysis"
as a substitute for running trailmark. Install it first. If installation
fails, report the error instead of switching to manual analysis.
A mutation testing framework for the target language — if the framework
command fails (not found, not installed), install it using the instructions
in references/mutation-frameworks.md.
DO NOT fall back to "manual mutation analysis" or skip mutation testing.
Install the framework first. If installation fails, report the error
instead of switching to manual mutation analysis.
necessist (optional, recommended) — if the target language is
supported (Go, Rust, Solidity/Foundry, TypeScript/Hardhat,
TypeScript/Vitest, Rust/Anchor), install with cargo install necessist.
See references/mutation-frameworks.md