more tests

src/ai.rs

@@ -245,9 +245,8 @@ fn alphabeta_with_printing_inner(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::board::view::View;
     use crate::board::{BitBoard, Board, Score};
-    use crate::game::Game;
+    use crate::game::{Game, Team};
 
     use rand::prelude::IndexedRandom;
     use rand::rngs::StdRng;
@@ -259,25 +258,72 @@ mod tests {
         *moves.choose(rng).unwrap()
     }
 
+    fn game_after(moves: &[Board]) -> Game {
+        let mut game = Game::default();
+        for &mv in moves {
+            game.safe_play(mv).expect("Move should be valid");
+        }
+        game
+    }
+
+    fn assert_ai_move_is_legal(game: &Game, depth: u8) -> Board {
+        let available = game.available();
+        let best_move = alphabeta(game.clone(), depth, i8::MIN + 1, i8::MAX - 1).0;
+        assert_ne!(best_move, 0, "AI should return a move when one exists");
+        assert_eq!(
+            best_move & available,
+            best_move,
+            "AI returned an illegal move"
+        );
+        best_move
+    }
+
     #[test]
     // just a sanity check to ensure that my AI performs up to snuff with another popular engine
     fn opening() {
         let mut game = Game::default();
-
-        println!("{}", game.board().render(View::RankAsc, vec![]));
         game.play(D3);
         let (best_move, _) = alphabeta(game.clone(), 12, i8::MIN + 1, i8::MAX - 1);
-        println!(
-            "dis:\n{}",
-            BitBoard {
-                boards: [0, best_move]
-            }
-        );
-        game.play(best_move);
-        println!("{}", game.board().render(View::RankAsc, vec![]));
         assert_eq!(best_move, C3);
     }
 
+    #[test]
+    fn ai_returns_legal_moves_across_curated_positions() {
+        let cases = vec![
+            (game_after(&[]), 4),
+            (game_after(&[D3]), 4),
+            (game_after(&[F5, F6, E6, F4]), 4),
+        ];
+
+        for (game, depth) in cases {
+            let available = game.available();
+            if available == 0 {
+                continue;
+            }
+            let mv = assert_ai_move_is_legal(&game, depth);
+            assert_ne!(mv, 0);
+        }
+    }
+
+    #[test]
+    fn ai_prefers_forced_corner() {
+        let board = BitBoard::from_jon("5bw//////").expect("Valid board");
+        let game = Game::from_parts(Team::Black, board);
+        assert_eq!(game.available(), H8);
+        let mv = assert_ai_move_is_legal(&game, 3);
+        assert_eq!(mv, H8);
+    }
+
+    #[test]
+    fn ai_passes_when_no_moves_exist() {
+        let board = BitBoard::from_jon("wwwwwwww/wwwwwwww/////").expect("Valid board");
+        let game = Game::from_parts(Team::Black, board);
+        assert_eq!(game.available(), 0);
+        let (mv, eval) = alphabeta(game.clone(), 4, i8::MIN + 1, i8::MAX - 1);
+        assert_eq!(mv, 0);
+        assert_eq!(eval, game.score().diff());
+    }
+
     // I found that, despite the AI clobbering me, the AI could not
     // compete with itself very well. I'm honestly not quite sure why that is.
     #[test]
@@ -310,6 +356,7 @@ mod tests {
                 } else {
                     random_move(&game, &mut rng)
                 };
+                assert_eq!(mv & game.available(), mv, "AI generated an illegal move");
                 game.play(mv);
             }