use super::SlotGenerations;
use types::generation::Generation;

#[test]
fn slots_start_at_the_initial_generation() {
    let g: SlotGenerations<2> = SlotGenerations::new();
    assert_eq!(g.current(0), Some(Generation::initial()));
    assert!(g.is_usable(1));
}

#[test]
fn advance_changes_the_generation() {
    let mut g: SlotGenerations<2> = SlotGenerations::new();
    let before = g.current(0);
    g.advance(0);
    assert_ne!(g.current(0), before);
    assert_eq!(g.current(1), before, "other slots untouched");
}

#[test]
fn out_of_range_slots_are_never_usable() {
    let mut g: SlotGenerations<2> = SlotGenerations::new();
    assert_eq!(g.current(2), None);
    g.advance(2); // no panic
}

#[test]
fn exhausted_counter_retires_the_slot() {
    let mut g: SlotGenerations<1> = SlotGenerations::new();
    g.gens[0] = Some(Generation::from_raw(u32::MAX));
    g.advance(0);
    assert_eq!(g.current(0), None);
    assert!(!g.is_usable(0));
    g.advance(0);
    assert_eq!(g.current(0), None, "retired slots stay retired");
}