Function install_pinned_cli_with 

pub fn install_pinned_cli_with(
    paths: &DataPaths,
    req: &NpmInstallRequest,
    on_line: &dyn Fn(&'static str, &str),
    run_npm: impl FnOnce(&Path, &str, bool) -> Result<NpmRun>,
) -> Result<InstallOutcome, InstallError>

install_pinned_cli with the npm runner injected (tests).