Function classify_red_one 

pub fn classify_red_one(
    result: &CheckResult,
    summary: Option<&RunnerSummary>,
    test: &str,
) -> RedClass

The class of the one test test from a run of the command that is to run only it: by name from a per-test report; without one, from the runner’s summary only when it ran exactly one test — a run of several tests cannot say which of them failed, so it is RedClass::Unclassified, never an assertion of test’s.