Function run 

pub fn run<S, R: Sides>(
    stage: &S,
    entrants: &[&dyn Entrant<S, R>],
    tries: &Tries,
    checks: &[Check],
) -> Result<PlaytestReport, PlaytestError<R>>
where
    R::Command: Clone,
    R::Outcome: Debug,

Every one of entrants plays stage as tries says, and checks judge their tries. A check naming an entrant not in the run fails before any try is played; a refused command stops the run.