Mutation Testing

Mutation Testing — Campaign Configuration (mewt/muton)

> Note: muton and mewt share identical interfaces but target different languages — mewt for general-purpose languages (Rust, Solidity, Go, TypeScript, JavaScript), muton for TON smart contracts (Tact, Tolk, FunC). All examples use mewt commands, but they work exactly the same with muton. File names change accordingly: mewt.toml → muton.toml, mewt.sqlite → muton.sqlite.

When to Use

Use this skill when the user:

• Mentions "mewt", "muton", or "mutation testing"
• Needs to configure or optimize a mutation testing campaign
• Wants to run mewt run and needs help getting set up first

When NOT to Use

Do not use this skill when the user:

• Wants to analyze or report on completed campaign results
• Asks about tests or coverage without mentioning mutation testing

Quick Start

Load workflows/configuration.md — a 5-phase guide from mewt init to a validated, ready-to-run campaign.

General question or unfamiliar command?

Run mewt --help or mewt <subcommand> --help, then assist.

Reference Index

| File | Content |

|------|---------|

| workflows/configuration.md | 5-phase guide: init, scope, optimize, validate, run |

| references/optimization-strategies.md | Per-file targeting, two-phase campaigns, mutation type filtering |

Essential Commands

# Initialize and mutate
mewt init                    # Create mewt.toml and mewt.sqlite
mewt mutate [paths]          # Generate mutants without running tests
mewt run [paths]             # Run the full campaign

# Inspect configuration and scope
mewt print config            # View effective configuration
mewt print targets           # Table of all targeted files
mewt print mutations --language [lang]  # Available mutation types
mewt status                  # Mutant count and per-file breakdown

# Investigate specific mutants
mewt print mutants --target [path]   # All mutants for a file
mewt print mutants --severity high   # Filter by severity
mewt print mutant --id [id]          # View mutated code diff
mewt test --ids [ids]                # Re-test specific mutants

What Results Mean

• Caught/TestFail: Tests detected the mutation (good)
• Uncaught: Mutation survived — indicates untested logic
• Timeout: Tests took too long, inconclusive
• Skipped: A more severe mutant already failed on the same line