irradiate¶

Fast mutation testing for Python, written in Rust.

irradiate finds gaps in your test suite by modifying your code and checking whether your tests catch the changes. A test suite that passes with mutated code has a surviving mutant, a blind spot where bugs can hide.

Why irradiate?¶

Mutation testing is slow because most tools invoke pytest from scratch for every mutant. Hundreds of cold starts, hundreds of seconds of overhead. irradiate keeps a pool of pre-warmed pytest workers alive and forks a child for each mutant. Pytest starts once. Tests run many times.

The parser uses tree-sitter with 27 mutation operator categories and runs in parallel via rayon. Results are cached with SHA-256 content addressing, so they survive rebases and branch switches. Incremental mode (--diff main) restricts testing to changed functions. Reports come in JSON (Stryker schema v2), HTML, and GitHub Actions annotations.

Quick start¶

pip install irradiate

irradiate run --paths-to-mutate src/
irradiate results
irradiate show mymodule.x_my_function__irradiate_1

For a complete walkthrough, see the Quick Start guide.