chessfriend/position/tests/peterellisjones.rs

// Eryn Wells <eryn@erynwells.me>

//! Move generator tests based on board positions described in [Peter Ellis
//! Jones][1]' excellent [blog post][2] on generated legal chess moves.
//!
//! [1]: https://peterellisjones.com
//! [2]: https://peterellisjones.com/posts/generating-legal-chess-moves-efficiently/

use chessfriend_core::Color;
use chessfriend_moves::{
    Move, assert_move_list, assert_move_list_contains, assert_move_list_does_not_contain, ply,
};
use chessfriend_position::test_position;
use std::collections::HashSet;

#[test]
fn pseudo_legal_move_generation() {
    let pos = test_position!(Black, [
        Black King on E8,
        White King on E1,
        White Rook on F5,
    ]);

    let king_moves: HashSet<_> = pos.all_legal_moves(Some(Color::Black)).collect();

    assert_move_list_does_not_contain!(king_moves, [ply!(E8 - F8), ply!(E8 - F7)]);
}

#[test]
fn gotcha_king_moves_away_from_checking_slider() {
    let position = test_position!(Black, [
        Black King on E7,
        White King on E1,
        White Rook on E4,
    ]);

    let king_moves: HashSet<Move> = position.all_legal_moves(None).map(Move::from).collect();

    assert_move_list_does_not_contain!(king_moves, [ply!(E7 - E8)]);
}

#[test]
fn check_evasions_1() {
    let pos = test_position!(Black, [
        Black King on E8,
        White King on E1,
        White Knight on F6,
    ]);

    let generated_moves = pos.all_legal_moves(Some(Color::Black));

    assert_move_list!(
        generated_moves,
        [ply!(E8 - D8), ply!(E8 - E7), ply!(E8 - F7), ply!(E8 - F8),]
    );
}

#[test]
fn check_evasions_double_check() {
    let pos = test_position!(Black, [
        Black King on E8,
        Black Bishop on F6,
        White King on E1,
        White Knight on G7,
        White Rook on E5,
    ]);

    let generated_moves = pos.all_legal_moves(Some(Color::Black));

    assert_move_list!(
        generated_moves,
        [ply!(E8 - D8), ply!(E8 - D7), ply!(E8 - F7), ply!(E8 - F8),]
    );
}

#[test]
fn single_check_with_blocker() {
    let pos = test_position!(Black, [
        Black King on E8,
        Black Knight on G6,
        White King on E1,
        White Rook on E5,
    ]);

    let generated_moves = pos.all_legal_moves(Some(Color::Black));

    assert_move_list!(
        generated_moves,
        [
            // King moves
            ply!(E8 - D8),
            ply!(E8 - D7),
            ply!(E8 - F7),
            ply!(E8 - F8),
            // Knight moves
            ply!(G6 - E7),
            ply!(G6 x E5),
        ]
    );
}

#[test]
fn en_passant_check_capture() {
    let pos = test_position!(Black, [
        Black King on C5,
        Black Pawn on E4,
        White Pawn on D4,
    ], D3);

    assert!(pos.board().is_in_check());

    let generated_moves: HashSet<_> = pos.all_legal_moves(Some(Color::Black)).collect();

    assert_move_list_contains!(generated_moves, [ply!(E4 x D3 e.p.)]);
}

#[test]
fn en_passant_check_block() {
    let pos = test_position!(Black, [
        Black King on B5,
        Black Pawn on E4,
        White Pawn on D4,
        White Queen on F1,
    ], D3);

    assert!(pos.board().is_in_check());

    let generated_moves: HashSet<_> = pos.all_legal_moves(Some(Color::Black)).collect();

    assert_move_list_contains!(generated_moves, [ply!(E4 x D3 e.p.)]);
}

#[test]
fn pinned_pieces_rook_cannot_move_out_of_pin() {
    let pos = test_position!(Black, [
        Black King on E8,
        Black Rook on E6,
        White Queen on E3,
        White King on C1,
    ]);

    assert!(!pos.board().is_in_check());

    let rook_moves: HashSet<_> = pos.all_legal_moves(None).collect();

    assert_move_list_does_not_contain!(rook_moves, [ply!(E6 - D6), ply!(E6 - F6)]);

    assert_move_list_contains!(
        rook_moves,
        [ply!(E6 x E3), ply!(E6 - E4), ply!(E6 - E5), ply!(E6 - E7)]
    );
}

#[test]
fn en_passant_discovered_check() {
    let pos = test_position!(Black, [
        Black King on A4,
        Black Pawn on E4,
        White Pawn on D4,
        White Queen on H4,
    ], D3);

    let generated_moves: HashSet<_> = pos.all_legal_moves(Some(Color::Black)).collect();

    assert_move_list_does_not_contain!(generated_moves, [ply!(E4 x D3 e.p.)]);
}