rust-clippy/tests/fmt.rs

#[test]
fn fmt() {
    if option_env!("RUSTC_TEST_SUITE").is_some() {
        return;
    }

    let root_dir = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"));
    let dev_dir = root_dir.join("clippy_dev");
    let output = std::process::Command::new("cargo")
        .current_dir(dev_dir)
        .args(&["+nightly", "run", "--", "fmt", "--check"])
        .output()
        .unwrap();

    println!("status: {}", output.status);
    println!("stdout: {}", String::from_utf8_lossy(&output.stdout));
    println!("stderr: {}", String::from_utf8_lossy(&output.stderr));

    assert!(
        output.status.success(),
        "Formatting check failed. Run `./util/dev fmt` to update formatting."
    );
}