mutate

A testing method that deliberately makes small changes to source code to check whether the test suite catches them.

In plain words
What is it for?
Use it to measure test effectiveness, find surviving code changes, identify missing test cases, and save a mutation report.
Why use it?
A passing test suite can still miss real bugs. Mutation testing reveals weak tests by listing changes that survived.

Command

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 commands/aegntic/cldcde/mutate
Clone the repo
git clone --depth 1 https://github.com/aegntic/cldcde
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 304 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 $0.00000 $0.00304
Opus 5 $0.00000 $0.00152
Sonnet 5 $0.00000 $0.00061
Haiku 4.5 $0.00000 $0.00030

Measured 2d ago against content hash be572625480c, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mutate 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.

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.

plugins/mutation-tester/commands/mutate.md · 29 lines

What it actually says

/mutate - Run Mutation Testing

Run mutation testing to evaluate test suite effectiveness.

Steps

  1. Detect the project language and testing framework from configuration files
  2. Check if a mutation testing tool is installed (Stryker for JS/TS, mutmut for Python, PITest for Java)
  3. If not installed, provide installation instructions for the appropriate tool
  4. Identify the source files and their corresponding test files
  5. Configure mutation operators: arithmetic, conditional, string, return value mutations
  6. Run the mutation testing tool on the target source files
  7. Monitor progress: total mutants generated, killed, survived, timed out
  8. Calculate the mutation score (killed / total * 100)
  9. List survived mutants with file location, line number, and mutation description
  10. For each survived mutant, identify which test should have caught it
  11. Suggest specific test cases to write for the top 10 survived mutants
  12. Save the mutation report to the reports directory

Rules

  • Start with a single file or module to keep execution time reasonable
  • Set a timeout per mutant of 10x the normal test execution time
  • Exclude test files, configuration files, and generated code from mutation
  • A mutation score below 80% indicates weak test coverage
  • Focus on survived mutants in critical business logic first
  • Do not count equivalent mutants (mutations that produce identical behavior)
  • Report execution time and mutant count for performance tracking
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 · 29 lines · 0 tokens per session scan A be572625480c

Subscribe to this mod's changes

mutate is a command published in the GitHub repository aegntic/cldcde (11 stars, last pushed 5d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 304 tokens. 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.