From 9a4fa827f987ea56041fc1afaa3172a4e89fcc52 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Wed, 21 May 2025 09:51:16 -0700
Subject: [PATCH] [position] Add two new negative tests for making pawn moves

- Ensure you cannot move a pawn to the last rank without a promotion move.
- Ensure a pawn cannot make an illegal move, and that the board state remains
  as it was before the move was attempted.
---
 position/src/position/make_move.rs | 59 +++++++++++++++++++++++++-----
 1 file changed, 50 insertions(+), 9 deletions(-)

diff --git a/position/src/position/make_move.rs b/position/src/position/make_move.rs
index fcefc24..e8502e9 100644
--- a/position/src/position/make_move.rs
+++ b/position/src/position/make_move.rs
@@ -1,8 +1,8 @@
 // Eryn Wells <eryn@erynwells.me>
 
 use crate::{movement::Movement, Position};
-use chessfriend_board::{en_passant, CastleParameters, PlacePieceError, PlacePieceStrategy};
-use chessfriend_core::{Color, Piece, Rank, Shape, Square, Wing};
+use chessfriend_board::{PlacePieceError, PlacePieceStrategy};
+use chessfriend_core::{Color, Piece, Rank, Square, Wing};
 use chessfriend_moves::Move;
 use thiserror::Error;
 
@@ -55,6 +55,9 @@ pub enum MakeMoveError {
 
     #[error("cannot promote on {0}")]
     InvalidPromotion(Square),
+
+    #[error("move to {0} requires promotion")]
+    PromotionRequired(Square),
 }
 
 pub enum UnmakeMoveError {}
@@ -70,7 +73,7 @@ impl Position {
         self.validate_move(ply, validate)?;
 
         if ply.is_quiet() {
-            return self.make_quiet_move(ply.origin_square(), ply.target_square());
+            return self.make_quiet_move(ply);
         }
 
         if ply.is_double_push() {
@@ -98,13 +101,17 @@ impl Position {
 }
 
 impl Position {
-    fn make_quiet_move(&mut self, origin: Square, target: Square) -> MakeMoveResult {
+    fn make_quiet_move(&mut self, ply: Move) -> MakeMoveResult {
+        let origin = ply.origin_square();
+
         let piece = self
-            .board
-            .remove_piece(origin)
+            .get_piece(origin)
             .ok_or(MakeMoveError::NoPiece(origin))?;
 
-        self.place_active_piece(piece, target)?;
+        let target = ply.target_square();
+        self.place_piece_for_move(piece, target)?;
+
+        self.remove_piece(origin);
 
         self.advance_clocks(HalfMoveClock::Advance);
 
@@ -119,7 +126,7 @@ impl Position {
             .ok_or(MakeMoveError::NoPiece(origin))?;
 
         let target = ply.target_square();
-        self.place_active_piece(piece, target)?;
+        self.place_piece_for_move(piece, target)?;
 
         self.board.en_passant_target = match target.rank() {
             Rank::FOUR => Some(Square::from_file_rank(target.file(), Rank::THREE)),
@@ -223,7 +230,11 @@ impl Position {
         self.get_piece(square).ok_or(MakeMoveError::NoPiece(square))
     }
 
-    fn place_active_piece(&mut self, piece: Piece, square: Square) -> MakeMoveResult {
+    fn place_piece_for_move(&mut self, piece: Piece, square: Square) -> MakeMoveResult {
+        if piece.is_pawn() && square.rank().is_promotable_rank() {
+            return Err(MakeMoveError::PromotionRequired(square));
+        }
+
         self.place_piece(piece, square, PlacePieceStrategy::PreserveExisting)
             .map_err(MakeMoveError::PlacePieceError)
     }
@@ -340,6 +351,20 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn make_invalid_quiet_pawn_move() {
+        let mut pos = test_position!(White Pawn on C2);
+
+        let ply = Move::quiet(Square::C2, Square::D2);
+        let result = pos.make_move(ply, ValidateMove::Yes);
+
+        assert!(result.is_err());
+        assert_eq!(pos.get_piece(Square::C2), Some(piece!(White Pawn)));
+        assert_eq!(pos.get_piece(Square::D2), None);
+        assert_eq!(pos.board.active_color, Color::White);
+        assert_eq!(pos.board.half_move_clock, 0);
+    }
+
     #[test]
     fn make_capture_move() {
         let mut pos = test_position![
@@ -391,6 +416,22 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn make_last_rank_quiet_move_without_promotion() {
+        let mut pos = test_position!(
+            White Pawn on A7
+        );
+
+        let ply = Move::quiet(Square::A7, Square::A8);
+        let result = pos.make_move(ply, ValidateMove::Yes);
+
+        assert!(result.is_err());
+        assert_eq!(pos.board.active_color, Color::White);
+        assert_eq!(pos.get_piece(Square::A7), Some(piece!(White Pawn)));
+        assert_eq!(pos.get_piece(Square::A8), None);
+        assert_eq!(pos.board.half_move_clock, 0);
+    }
+
     #[test]
     fn make_promotion_move() -> MakeMoveResult {
         let mut pos = test_position![