lnds's solution

poker.rs

use poker::winning_hands;
use std::collections::HashSet;

fn hs_from<'a>(input: &[&'a str]) -> HashSet<&'a str> {
    let mut hs = HashSet::new();
    for item in input.iter() {
        hs.insert(*item);
    }
    hs
}

/// Test that the expected output is produced from the given input
/// using the `winning_hands` function.
///
/// Note that the output can be in any order. Here, we use a HashSet to
/// abstract away the order of outputs.
fn test<'a, 'b>(input: &[&'a str], expected: &[&'b str]) {
    assert_eq!(
        hs_from(&winning_hands(input).expect("This test should produce Some value",)),
        hs_from(expected)
    )
}

#[test]
fn test_single_hand_always_wins() {
    test(&["4S 5S 7H 8D JC"], &["4S 5S 7H 8D JC"])
}

#[test]
#[ignore]
fn test_highest_card_of_all_hands_wins() {
    test(
        &["4D 5S 6S 8D 3C", "2S 4C 7S 9H 10H", "3S 4S 5D 6H JH"],
        &["3S 4S 5D 6H JH"],
    )
}

#[test]
#[ignore]
fn test_a_tie_has_multiple_winners() {
    test(
        &[
            "4D 5S 6S 8D 3C",
            "2S 4C 7S 9H 10H",
            "3S 4S 5D 6H JH",
            "3H 4H 5C 6C JD",
        ],
        &["3S 4S 5D 6H JH", "3H 4H 5C 6C JD"],
    )
}

#[test]
#[ignore]
fn test_high_card_can_be_low_card_in_an_otherwise_tie() {
    // multiple hands with the same high cards, tie compares next highest ranked,
    // down to last card
    test(&["3S 5H 6S 8D 7H", "2S 5D 6D 8C 7S"], &["3S 5H 6S 8D 7H"])
}

#[test]
#[ignore]
fn test_one_pair_beats_high_card() {
    test(&["4S 5H 6C 8D KH", "2S 4H 6S 4D JH"], &["2S 4H 6S 4D JH"])
}

#[test]
#[ignore]
fn test_highest_pair_wins() {
    test(&["4S 2H 6S 2D JH", "2S 4H 6C 4D JD"], &["2S 4H 6C 4D JD"])
}

#[test]
#[ignore]
fn test_two_pairs_beats_one_pair() {
    test(&["2S 8H 6S 8D JH", "4S 5H 4C 8C 5C"], &["4S 5H 4C 8C 5C"])
}

#[test]
#[ignore]
fn test_two_pair_ranks() {
    // both hands have two pairs, highest ranked pair wins
    test(&["2S 8H 2D 8D 3H", "4S 5H 4C 8S 5D"], &["2S 8H 2D 8D 3H"])
}

#[test]
#[ignore]
fn test_two_pairs_second_pair_cascade() {
    // both hands have two pairs, with the same highest ranked pair,
    // tie goes to low pair
    test(&["2S QS 2C QD JH", "JD QH JS 8D QC"], &["JD QH JS 8D QC"])
}

#[test]
#[ignore]
fn test_two_pairs_last_card_cascade() {
    // both hands have two identically ranked pairs,
    // tie goes to remaining card (kicker)
    test(&["JD QH JS 8D QC", "JS QS JC 2D QD"], &["JD QH JS 8D QC"])
}

#[test]
#[ignore]
fn test_three_of_a_kind_beats_two_pair() {
    test(&["2S 8H 2H 8D JH", "4S 5H 4C 8S 4H"], &["4S 5H 4C 8S 4H"])
}

#[test]
#[ignore]
fn test_three_of_a_kind_ranks() {
    //both hands have three of a kind, tie goes to highest ranked triplet
    test(&["2S 2H 2C 8D JH", "4S AH AS 8C AD"], &["4S AH AS 8C AD"])
}

#[test]
#[ignore]
fn test_three_of_a_kind_cascade_ranks() {
    // with multiple decks, two players can have same three of a kind,
    // ties go to highest remaining cards
    test(&["4S AH AS 7C AD", "4S AH AS 8C AD"], &["4S AH AS 8C AD"])
}

#[test]
#[ignore]
fn test_straight_beats_three_of_a_kind() {
    test(&["4S 5H 4C 8D 4H", "3S 4D 2S 6D 5C"], &["3S 4D 2S 6D 5C"])
}

#[test]
#[ignore]
fn test_aces_can_end_a_straight_high() {
    // aces can end a straight (10 J Q K A)
    test(&["4S 5H 4C 8D 4H", "10D JH QS KD AC"], &["10D JH QS KD AC"])
}

#[test]
#[ignore]
fn test_aces_can_end_a_straight_low() {
    // aces can start a straight (A 2 3 4 5)
    test(&["4S 5H 4C 8D 4H", "4D AH 3S 2D 5C"], &["4D AH 3S 2D 5C"])
}

#[test]
#[ignore]
fn test_straight_cascade() {
    // both hands with a straight, tie goes to highest ranked card
    test(&["4S 6C 7S 8D 5H", "5S 7H 8S 9D 6H"], &["5S 7H 8S 9D 6H"])
}

#[test]
#[ignore]
fn test_straight_scoring() {
    // even though an ace is usually high, a 5-high straight is the lowest-scoring straight
    test(&["2H 3C 4D 5D 6H", "4S AH 3S 2D 5H"], &["2H 3C 4D 5D 6H"])
}

#[test]
#[ignore]
fn test_flush_beats_a_straight() {
    test(&["4C 6H 7D 8D 5H", "2S 4S 5S 6S 7S"], &["2S 4S 5S 6S 7S"])
}

#[test]
#[ignore]
fn test_flush_cascade() {
    // both hands have a flush, tie goes to high card, down to the last one if necessary
    test(&["4H 7H 8H 9H 6H", "2S 4S 5S 6S 7S"], &["4H 7H 8H 9H 6H"])
}

#[test]
#[ignore]
fn test_full_house_beats_a_flush() {
    test(&["3H 6H 7H 8H 5H", "4S 5C 4C 5D 4H"], &["4S 5C 4C 5D 4H"])
}

#[test]
#[ignore]
fn test_full_house_ranks() {
    // both hands have a full house, tie goes to highest-ranked triplet
    test(&["4H 4S 4D 9S 9D", "5H 5S 5D 8S 8D"], &["5H 5S 5D 8S 8D"])
}

#[test]
#[ignore]
fn test_full_house_cascade() {
    // with multiple decks, both hands have a full house with the same triplet, tie goes to the pair
    test(&["5H 5S 5D 9S 9D", "5H 5S 5D 8S 8D"], &["5H 5S 5D 9S 9D"])
}

#[test]
#[ignore]
fn test_four_of_a_kind_beats_full_house() {
    test(&["4S 5H 4D 5D 4H", "3S 3H 2S 3D 3C"], &["3S 3H 2S 3D 3C"])
}

#[test]
#[ignore]
fn test_four_of_a_kind_ranks() {
    // both hands have four of a kind, tie goes to high quad
    test(&["2S 2H 2C 8D 2D", "4S 5H 5S 5D 5C"], &["4S 5H 5S 5D 5C"])
}

#[test]
#[ignore]
fn test_four_of_a_kind_cascade() {
    // with multiple decks, both hands with identical four of a kind, tie determined by kicker
    test(&["3S 3H 2S 3D 3C", "3S 3H 4S 3D 3C"], &["3S 3H 4S 3D 3C"])
}

#[test]
#[ignore]
fn test_straight_flush_beats_four_of_a_kind() {
    test(&["4S 5H 5S 5D 5C", "7S 8S 9S 6S 10S"], &["7S 8S 9S 6S 10S"])
}

#[test]
#[ignore]
fn test_straight_flush_ranks() {
    // both hands have straight flush, tie goes to highest-ranked card
    test(&["4H 6H 7H 8H 5H", "5S 7S 8S 9S 6S"], &["5S 7S 8S 9S 6S"])
}