Gambit vs pytest-gremlins

Gambit is a free, open-source mutation testing tool for Solidity projects. It generates altered contract versions, called mutants, to measure whether a test suite or formal verification specification detects faults. Gambit locates mutation points by traversing a program’s abstract syntax tree and applying predefined syntax transformations. A declarative configuration language lets users tailor mutations to specific parts of a program. Results can be viewed in a dashboard that summarizes mutant verification and calculates a specification score. Gambit can work with the Certora Prover to evaluate formal specifications; that workflow generates mutants and submits a verification job for each to Certora’s server. The command line includes `mutate` for generating mutants and `summary` for presenting them. A compatible `solc` binary is required for the project being mutated. Gambit supports Solidity and is listed for Linux, macOS, and Windows, though prebuilt binaries are available for Linux x86-64 and Mac; Windows and Linux ARM users must build from source. Function-call and swap-arguments-function mutation operators are disabled. The repository identifies the license as MIT. Certora directs product questions to its Help Desk channel on Discord.

pytest-gremlins is a pytest plugin for checking whether an existing test suite catches small changes to code. It runs mutation tests against Python projects and can report results in the console, HTML, or JSON, including multiple formats in one run. Getting started requires Python 3.11 or later, pytest 7.0 or later, and existing tests; installation is documented with pip, uv, and Poetry. The project’s quick-start command is `pytest --gremlins`. To manage execution, it uses mutation switching, coverage-guided test selection, incremental analysis, and parallel execution, and it works with pytest-xdist. Options can be set in `pyproject.toml` or with command-line flags, while inline pragmas can pardon specific mutations. A GitHub Action can run the checks and fail a workflow if its score misses a threshold; CI examples also cover GitLab CI, CircleCI, and Dagger. It is a free, MIT-licensed package for Linux, classified as Alpha. The guide warns that an initial run may take 10–100 times as long as a normal test run, though caching can shorten later runs. It also notes that equivalent mutations can make a perfect score unattainable and unnecessary.