Add attacker and check logic with tests

test/test_attack_to.py

@@ -0,0 +1,100 @@
+import ctypes
+from test.base import ChessLibTestBase
+from test.chess_ffi import get_attackers_to
+from test.chess_ffi import is_square_attacked
+from test.chess_ffi import is_in_check
+from test.chess_ffi import sq
+from test.chess_ffi import Board
+from test.chess_ffi import BLACK
+from test.chess_ffi import WHITE
+from test.chess_ffi import draw_bb
+
+
+class TestAttackers(ChessLibTestBase):
+    def test_square_attacked(self):
+        cases = [
+            # Pawns: bp d5 attacks c4/e4; not d4
+            ("8/8/8/3p4/8/8/8/8 w - - 0 1", "c4", BLACK, True,  "bp d5 -> c4"),
+            ("8/8/8/3p4/8/8/8/8 w - - 0 1", "e4", BLACK, True,  "bp d5 -> e4"),
+            ("8/8/8/3p4/8/8/8/8 w - - 0 1", "d4", BLACK, False, "bp d5 not d4"),
+
+            # Knights
+            ("8/8/8/3n4/8/8/8/8 w - - 0 1", "f4", BLACK, True,  "bn d5 -> f4"),
+            ("8/8/8/3n4/8/8/8/8 w - - 0 1", "e7", BLACK, True,  "bn d5 -> e7"),
+            ("8/8/8/3n4/8/8/8/8 w - - 0 1", "e5", BLACK, False, "bn d5 not e5"),
+
+            # Bishops (wB d4)
+            ("8/8/8/8/3B4/8/8/8 w - - 0 1", "c5", WHITE, True,  "wB d4 -> c5"),
+            ("8/8/8/8/3B4/8/8/8 w - - 0 1", "e5", WHITE, True,  "wB d4 -> e5"),
+
+            # Rooks (wR e4)
+            ("8/8/8/8/4R3/8/8/8 w - - 0 1", "e8", WHITE, True,  "wR e4 -> e8 clear"),
+            ("4k3/4p3/8/8/4R3/8/8/8 w - - 0 1", "e8", WHITE, False, "wR e4 blocked by pe7"),
+            ("4k3/4p3/8/8/4R3/8/8/8 w - - 0 1", "e7", WHITE, True, "wR e4 blocked can attack pawn on e7"),
+            ("8/8/8/8/4R3/8/8/8 w - - 0 1", "a4", WHITE, True,  "wR e4 -> a4"),
+
+            # Queens (wQ d4)
+            ("8/8/8/8/3Q4/8/8/8 w - - 0 1", "h8", WHITE, True,  "wQ d4 -> h8"),
+            ("8/8/8/8/3Q4/8/8/8 w - - 0 1", "d8", WHITE, True,  "wQ d4 -> d8"),
+
+            # Kings (bk e4)
+            ("8/8/8/8/4k3/8/8/4K3 w - - 0 1", "e3", BLACK, True,  "bk e4 -> e3"),
+            ("8/8/8/8/4k3/8/8/4K3 w - - 0 1", "g4", BLACK, False, "bk e4 not g4"),
+
+            # Edge knights (bn a1)
+            ("8/8/8/8/8/8/8/n7 w - - 0 1", "b3", BLACK, True,  "bn a1 -> b3"),
+            ("8/8/8/8/8/8/8/n7 w - - 0 1", "c2", BLACK, True,  "bn a1 -> c2"),
+            ("8/8/8/8/8/8/8/n7 w - - 0 1", "a2", BLACK, False, "bn a1 not a2"),
+        ]
+
+        for fen, sq_str, by, expected, msg in cases:
+            with self.subTest(msg=msg, fen=fen, sq=sq_str, by=by):
+                b = Board()
+                self.load_fen(fen, board=b)
+                got = bool(is_square_attacked(b, sq(sq_str), by))
+                self.assertEqual(expected, got, msg)
+
+
+    def test_in_check(self):
+        cases = [
+            # Unblocked slider (Qe2 checks e8)
+            ("4k3/8/8/8/8/8/4Q3/4K3 b - - 0 1", BLACK, True,  "Qe2 -> e8"),
+            # Blocked by pe7
+            ("4k3/4p3/8/8/8/8/4Q3/4K3 b - - 0 1", BLACK, False, "Qe2 blocked by pe7"),
+
+            # Knight check (Nc7 checks e8)
+            ("4k3/2N5/8/8/8/8/8/4K3 b - - 0 1", BLACK, True,  "Nc7 -> e8"),
+
+            # Pawn check: bp e5 checks f4 (WK on f4)
+            ("4k3/8/8/4p3/5K2/8/8/8 b - - 0 1", WHITE, True,  "bp e5 -> f4"),
+            # Not checking WK e1
+            ("4k3/8/8/4p3/8/8/8/4K3 b - - 0 1", WHITE, False, "bp e5 not e1"),
+
+            # King adjacency (illegal but detected)
+            # Ensure that this case does not make it through a legality filter.
+            ("8/8/8/8/8/8/4k3/4K3 w - - 0 1", WHITE, True,  "BK e2 checks WK e1"),
+
+            # Double check (Qe2 + Nc7 vs BK e8)
+            ("4k3/2N5/8/8/8/8/4Q3/4K3 b - - 0 1", BLACK, True,  "double check still true"),
+        ]
+
+        for fen, side, expected, msg in cases:
+            with self.subTest(msg=msg, fen=fen, side=side):
+                b = Board()
+                self.load_fen(fen, board=b)
+                actual = bool(is_in_check(b, side))
+                self.assertEqual(expected, actual, msg)
+
+    def test_attackers_to_popcount(self):
+        cases = [
+            # Bishop on d4, adjacent enemies on each ray → 4 attackers
+            ("8/8/8/2p1p3/3B4/2p1p3/8/8 w - - 0 1", "d4", BLACK, 2, "adjacent enemies on c5,e5,c3,e3"),
+        ]
+
+        for fen, sq_str, by, expected_cnt, msg in cases:
+            with self.subTest(msg=msg, fen=fen, sq=sq_str, by=by):
+                b = Board()
+                self.load_fen(fen, board=b)
+
+                mask = get_attackers_to(b, sq(sq_str), by)
+                self.assertEqual(expected_cnt, int(mask).bit_count())