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test: add comprehensive check detection and castling tests
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‎src/test/kotlin/dev/tabansi/chess/CastlingTest.kt‎

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package dev.tabansi.chess
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import dev.tabansi.chess.Board.EMPTY
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import dev.tabansi.chess.Board.KING
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import dev.tabansi.chess.Board.PLAYER_1
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import dev.tabansi.chess.Board.PLAYER_2
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import dev.tabansi.chess.Board.ROOK
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import dev.tabansi.chess.Board.board
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import dev.tabansi.chess.pieces.King
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import kotlin.test.Test
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import kotlin.test.assertFalse
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import kotlin.test.assertTrue
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class CastlingTest {
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private fun clearBoard() {
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for (i in 0 until 8) for (j in 0 until 8) board[i][j] = EMPTY
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}
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@Test
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fun white_kingside_castle_allowed_when_path_clear_and_safe() {
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clearBoard()
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val p1 = Player(PLAYER_1)
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// Place only king and rook in starting squares
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board[7][4] = KING + PLAYER_1
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board[7][7] = ROOK + PLAYER_1
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val moves = p1.king.getMoves()
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assertTrue(moves.contains(BoardSpace(7, 6)), "White should be able to castle king side when path is clear and safe")
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}
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@Test
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fun white_kingside_castle_disallowed_if_pass_through_square_attacked() {
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clearBoard()
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val p1 = Player(PLAYER_1)
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// King & rook on starting squares
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board[7][4] = KING + PLAYER_1
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board[7][7] = ROOK + PLAYER_1
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// Attack pass-through square (7,5) with an enemy rook on same file
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// Place enemy rook at (3,5) so it attacks (7,5) but not (7,4)
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board[3][5] = ROOK + PLAYER_2
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val moves = p1.king.getMoves()
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assertFalse(moves.contains(BoardSpace(7, 6)), "White castling should be disallowed if f1 (7,5) is attacked")
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}
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@Test
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fun white_kingside_castle_disallowed_if_final_square_attacked() {
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clearBoard()
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val p1 = Player(PLAYER_1)
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// King & rook on starting squares
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board[7][4] = KING + PLAYER_1
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board[7][7] = ROOK + PLAYER_1
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// Attack final square (7,6) with a bishop-like diagonal from (5,4)
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// Using a rook along diagonal is not possible; we simulate with an enemy queen that moves diagonally.
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board[5][4] = "QN" + PLAYER_2
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val moves = p1.king.getMoves()
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assertFalse(moves.contains(BoardSpace(7, 6)), "White castling should be disallowed if g1 (7,6) is attacked")
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}
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@Test
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fun black_queenside_castle_allowed_when_path_clear_and_safe() {
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clearBoard()
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val p2 = Player(PLAYER_2)
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// Place only king and rook in starting squares for black
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board[0][4] = KING + PLAYER_2
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board[0][0] = ROOK + PLAYER_2
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val moves = p2.king.getMoves()
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assertTrue(moves.contains(BoardSpace(0, 2)), "Black should be able to castle queen side when path is clear and safe")
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}
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}

‎src/test/kotlin/dev/tabansi/chess/CheckDetectionTest.kt‎

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package dev.tabansi.chess
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import dev.tabansi.chess.Board.BISHOP
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import dev.tabansi.chess.Board.EMPTY
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import dev.tabansi.chess.Board.KING
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import dev.tabansi.chess.Board.KNIGHT
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import dev.tabansi.chess.Board.PAWN
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import dev.tabansi.chess.Board.PLAYER_1
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import dev.tabansi.chess.Board.PLAYER_2
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import dev.tabansi.chess.Board.QUEEN
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import dev.tabansi.chess.Board.ROOK
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import dev.tabansi.chess.Board.board
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import dev.tabansi.chess.pieces.King
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import dev.tabansi.chess.pieces.Piece
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import kotlin.test.*
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class CheckDetectionTest {
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private fun clearBoard() {
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for (i in 0 until 8) for (j in 0 until 8) board[i][j] = EMPTY
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}
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private fun place(x: Int, y: Int, piece: String) {
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board[x][y] = piece
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}
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@Test
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fun rook_vertical_check_true_and_blocked_false() {
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clearBoard()
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val p1 = Player(PLAYER_1)
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val k = King(BoardSpace(4, 4), p1)
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place(4, 4, KING + PLAYER_1)
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// Enemy rook on same file with clear path -> check
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place(0, 4, ROOK + PLAYER_2)
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assertTrue(k.isInCheck(), "Rook on same file with no blockers should give check")
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// Block the line -> no check
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place(2, 4, PAWN + PLAYER_1)
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assertFalse(k.isInCheck(), "Blocked rook line should not give check")
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}
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@Test
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fun rook_horizontal_check_true_and_blocked_false() {
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clearBoard()
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val p2 = Player(PLAYER_2)
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val k = King(BoardSpace(3, 3), p2)
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place(3, 3, KING + PLAYER_2)
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// Enemy rook on same rank with clear path -> check
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place(3, 7, ROOK + PLAYER_1)
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assertTrue(k.isInCheck(), "Rook on same rank with no blockers should give check")
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// Block the line -> no check
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place(3, 5, PAWN + PLAYER_2)
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assertFalse(k.isInCheck(), "Blocked rook line should not give check")
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}
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@Test
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fun bishop_diagonal_check_true_and_blocked_false() {
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clearBoard()
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val p1 = Player(PLAYER_1)
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val k = King(BoardSpace(4, 4), p1)
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place(4, 4, KING + PLAYER_1)
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// Enemy bishop on clear diagonal -> check
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place(1, 1, BISHOP + PLAYER_2)
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assertTrue(k.isInCheck(), "Bishop on clear diagonal should give check")
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// Block the diagonal -> no check
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place(2, 2, PAWN + PLAYER_1)
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assertFalse(k.isInCheck(), "Blocked bishop diagonal should not give check")
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}
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@Test
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fun queen_sliding_check_true() {
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clearBoard()
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val p2 = Player(PLAYER_2)
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val k = King(BoardSpace(6, 6), p2)
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place(6, 6, KING + PLAYER_2)
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// Enemy queen on diagonal -> check
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place(4, 4, QUEEN + PLAYER_1)
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assertTrue(k.isInCheck(), "Queen on diagonal should give check")
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}
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@Test
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fun knight_check_true_and_false() {
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clearBoard()
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val p1 = Player(PLAYER_1)
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val k = King(BoardSpace(4, 4), p1)
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place(4, 4, KING + PLAYER_1)
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// Knight attacks from (5,6)
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place(5, 6, KNIGHT + PLAYER_2)
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assertTrue(k.isInCheck(), "Knight in L position should give check")
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// Move knight to a non-attacking square
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place(5, 6, EMPTY)
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place(5, 5, KNIGHT + PLAYER_2)
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assertFalse(k.isInCheck(), "Knight not in L position should not give check")
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}
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@Test
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fun pawn_threats_for_both_colors() {
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// P1 king attacked by P2 pawn from one row above (x-1, y±1)
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clearBoard()
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val p1 = Player(PLAYER_1)
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val k1 = King(BoardSpace(4, 4), p1)
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place(4, 4, KING + PLAYER_1)
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place(3, 3, PAWN + PLAYER_2) // attacks (4,4)
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assertTrue(k1.isInCheck(), "P2 pawn should threaten P1 king from (x-1, y-1)")
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// P2 king attacked by P1 pawn from one row below (x+1, y±1)
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clearBoard()
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val p2 = Player(PLAYER_2)
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val k2 = King(BoardSpace(3, 3), p2)
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place(3, 3, KING + PLAYER_2)
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place(4, 4, PAWN + PLAYER_1) // attacks (3,3)
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assertTrue(k2.isInCheck(), "P1 pawn should threaten P2 king from (x+1, y+1)")
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}
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@Test
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fun adjacent_king_threat_detected() {
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clearBoard()
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val p1 = Player(PLAYER_1)
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val k = King(BoardSpace(4, 4), p1)
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place(4, 4, KING + PLAYER_1)
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// Enemy king adjacent
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place(5, 5, KING + PLAYER_2)
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assertTrue(k.isInCheck(), "Adjacent enemy king should count as a check")
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}
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}

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