Function generate_test_harness

fn generate_test_harness(
    sess: &Session,
    resolver: &mut dyn ResolverExpand,
    reexport_test_harness_main: Option<Symbol>,
    krate: &mut Crate,
    features: &Features,
    panic_strategy: PanicStrategy,
    test_runner: Option<Path>,
)

Crawl over the crate, inserting test reexports and the test main function