From 1e77bc5ebb53e23c1e6e188ea30b256b4a1573bc Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Sun, 28 Jan 2024 09:45:13 -0800
Subject: [PATCH] [board] Test to verify the king can't move into or stay in
 check

Write a test on the king move generator to verify the king can't move to a
square where it would still be in check.
---
 board/src/move_generator/king.rs | 38 +++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/board/src/move_generator/king.rs b/board/src/move_generator/king.rs
index 1d0dda2..1f35af5 100644
--- a/board/src/move_generator/king.rs
+++ b/board/src/move_generator/king.rs
@@ -74,7 +74,7 @@ impl MoveGeneratorInternal for KingMoveGenerator {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::position;
+    use crate::{position, r#move::AlgebraicMoveFormatter, PositionBuilder};
     use chessfriend_bitboard::bitboard;
     use chessfriend_core::{piece, Square};
     use std::collections::HashSet;
@@ -154,4 +154,40 @@ mod tests {
             generated_moves
         );
     }
+
+    #[test]
+    fn black_king_in_check_by_rook() {
+        let pos = PositionBuilder::new()
+            .place_piece(piece!(White King on E1))
+            .place_piece(piece!(White Rook on E4))
+            .place_piece(piece!(Black King on E7))
+            .to_move(Color::Black)
+            .build();
+
+        assert!(pos.is_king_in_check());
+
+        let generator = KingMoveGenerator::new(&pos, Color::Black);
+        let generated_moves: HashSet<Move> = generator.iter().cloned().collect();
+
+        let king = piece!(Black King);
+        let from_square = Square::E7;
+        let expected_moves = HashSet::from_iter([
+            MoveBuilder::new(king, from_square, Square::D6).build(),
+            MoveBuilder::new(king, from_square, Square::D7).build(),
+            MoveBuilder::new(king, from_square, Square::D8).build(),
+            MoveBuilder::new(king, from_square, Square::F6).build(),
+            MoveBuilder::new(king, from_square, Square::F7).build(),
+            MoveBuilder::new(king, from_square, Square::F8).build(),
+        ]);
+
+        assert_eq!(
+            generated_moves,
+            expected_moves,
+            "Difference: {:?}",
+            generated_moves
+                .symmetric_difference(&expected_moves)
+                .map(|mv| format!("{}", AlgebraicMoveFormatter::new(mv, &pos)))
+                .collect::<Vec<_>>()
+        );
+    }
 }