MuTON

In genetics, a muton is the smallest unit of DNA that can produce a mutation.

muton runs mutation testing campaigns for TON smart contracts.

Supported languages are auto-detected by file extension:

• FunC (.fc, .func)
• Tact (.tact)
• Tolk (.tolk)

Installation

npm (recommended)

npm install -g @trailofbits/muton

Prebuilt binaries

curl --proto '=https' --tlsv1.2 -LsSf \
  https://github.com/trailofbits/muton/releases/latest/download/muton-installer.sh | sh

Build from source (native toolchain)

Requirements:

• Rust toolchain (via rustup)
• C toolchain (gcc/clang) and make
• pkg-config
• SQLite development headers (libsqlite3-dev/sqlite)

Build and run:

cargo build --release
./target/release/muton --help

Build from source (Nix)

With Nix flakes enabled:

git clone https://github.com/trailofbits/muton.git
cd muton
nix develop --command bash -c 'just build'
./target/debug/muton --version

Quick start

Initialize a workspace (creates muton.toml and muton.sqlite):

muton init

Run a campaign against a target file or directory:

muton run path/to/contract.tact --test.cmd "npx blueprint test"

Use globs when needed:

muton run "contracts/**/*.tact" --test.cmd "npx blueprint test"

Inspect campaign progress and outcomes:

muton status
muton results --all
muton results --status uncaught --severity high,medium

Inspect generated mutants:

muton print mutations --language tact
muton print mutants --target path/to/contract.tact
muton print mutant --id 42

Test all mutants even if more severe mutants on the same line were uncaught:

muton run path/to/contract.tact --comprehensive --test.cmd "npx blueprint test"

How muton works

Mutation campaigns can be slow. muton is designed to make them resumable and predictable:

• Targets and mutants are stored in a single SQLite database (muton.sqlite by default).
• Interrupted campaigns can resume where they left off.
• By default, less-severe mutants on a line may be skipped if a more-severe mutant on that same line was already uncaught.

[!TIP] Use --comprehensive to disable skip optimization and force testing of all generated mutants.

Because mutation testing is usually slow, it is commonly run periodically (for example, overnight) rather than on every commit.

Configuration

Configuration precedence (highest to lowest):

1. CLI flags
2. muton.toml
3. Built-in defaults

muton.toml is discovered by walking up from the current working directory. You can also pin a config file explicitly with --config path/to/muton.toml.

Print your effective configuration:

muton print config

Example config:

db = "muton.sqlite"

[log]
level = "info"
# color = true

[targets]
# include = ["contracts/**/*.tact", "contracts/**/*.func"]
# ignore = ["build", "node_modules"]

[run]
# mutations = ["ER", "CR"]
# comprehensive = false

[test]
# cmd = "npx blueprint test"
# timeout = 120

Example contracts in this repo

• FunC: tests/func/examples/hello-world.fc
• Tact: tests/tact/examples/hello-world.tact
• Tolk: tests/tolk/examples/hello-world.tolk

Notes

• Mixed-language projects are supported.
• Directory targets recurse automatically; only supported file extensions are considered.