Usage

To run mutest-rs on any Cargo package or workspace, use the cargo mutest run subcommand with the usual Cargo targeting options (see Cargo Package Selection, Cargo Target Selection, and Cargo Feature Selection):

cargo mutest -p example-package run

It is recommended to specify specific Cargo test targets to start with, using the standard --lib, --bin <BIN>, --test <TEST>, and --example <EXAMPLE> targeting options, alongside the -p <PACKAGE> option.

Prerequisites

The main cargo mutest subcommand provides a Cargo-compatible interface to mutest-rs for Cargo packages and workspaces. Generally speaking, as long as cargo test works for your package, then cargo mutest run will run the same test suite under mutation analysis.

Using cfg(mutest)

When running cargo mutest, the mutest cfg is set. This can be used to detect if code is running under mutest-rs, and enable conditional compilation based on it.

Starting with Rust 1.80, cfgs are checked against a known set of config names and values. If your Cargo package is checked with a regular Cargo command, it will warn you about the “unexpected” mutest cfg. To let rustc know that this custom cfg is expected, ensure that cfg(mutest) is present in the [lints.rust.unexpected_cfgs.check-cfg] array in the package’s Cargo.toml, like so:

[lints.rust]
unexpected_cfgs = { level = "warn", check-cfg = ["cfg(mutest)"] }