Function report 

pub fn report(
    session: &Session,
    cases: &[Case],
    outcomes: &[Outcome],
    options: ReportOptions<'_>,
) -> Report

Score the outcomes against the cases.

A case either answered everything it was labelled for or it counts as an error: a half-answered case would quietly skew whichever question it did answer, and a rubric is being judged here.