testing-conventions 0.0.42

//! Integration tests for the Rust mutation rule (#201).
//!
//! These run REAL `cargo mutants` over the fixture crates via the SDK
//! ([`mutation::measure_rust`]) and assert the surviving-mutant set. Per the #3
//! guardrail the *crates themselves* are the fixtures: `killed` (every mutant caught
//! by an asserting test) reports no survivors, and `survivors` (an assertion-light
//! test that runs the code but pins nothing) reports several — the gap mutation
//! testing exposes that coverage can't. Requires `cargo-mutants`.

use std::path::PathBuf;

use testing_conventions::mutation::measure_rust;

fn crate_dir(name: &str) -> PathBuf {
    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .join("tests/fixtures/unit_mutation/rust")
        .join(name)
}

#[test]
fn killed_reports_no_survivors() {
    let survivors = measure_rust(
        &crate_dir("killed"),
        &[],
        &std::collections::BTreeMap::new(),
        None,
    )
    .expect("cargo-mutants runs");
    assert!(
        survivors.is_empty(),
        "every mutant should be caught; got {survivors:?}"
    );
}

#[test]
fn survivors_are_reported() {
    let survivors = measure_rust(
        &crate_dir("survivors"),
        &[],
        &std::collections::BTreeMap::new(),
        None,
    )
    .expect("cargo-mutants runs");
    assert!(
        !survivors.is_empty(),
        "the assertion-light suite should leave survivors"
    );
    assert!(
        survivors.iter().all(|m| m.file == "src/lib.rs"),
        "every survivor is in src/lib.rs; got {survivors:?}"
    );
}

#[test]
fn a_mutation_exemption_drops_the_survivors() {
    // Exempting the survivors' file lifts all of them — an equivalent / deliberately
    // defensive mutation, waived with a reason via `[[rust.exempt]] rules = ["mutation"]`.
    let exempt = vec!["src/lib.rs".to_string()];
    let survivors = measure_rust(
        &crate_dir("survivors"),
        &exempt,
        &std::collections::BTreeMap::new(),
        None,
    )
    .expect("cargo-mutants runs");
    assert!(
        survivors.is_empty(),
        "the exemption should drop every survivor; got {survivors:?}"
    );
}