Swift

Board.swift

protocol Board {
    func isValidMove(move: (x: Int, y: Int)) -> Bool
}

Game.swift

class MoveGenerator {

    let board: BoardProtocol

    func forPosition(position: (x: Int, y: Int)) -> [(x: Int, y: Int)] {
        let move = (x: position.x, y: position.y)
        if self.board.isValidMove(move) {
            return [move]
        }
        
        return []
    }

    init(board: Board) {
        self.board = board
    }
}

MoveGeneratorTests.swift

class FullBoard: BoardProtocol {
    func isValidMove(move: (x: Int, y: Int)) -> Bool {
        return false
    }
}

class EmptyBoard: BoardProtocol {
    func isValidMove(move: (x: Int, y: Int)) -> Bool {
        return true
    }
}

class MoveGeneratorTests: XCTestCase {

    func testGeneratesEmptyList() {
        let generator = MoveGenerator(board: FullBoard())
        XCTAssertEqual(generator.forPosition((x: 0, y: 0)).count, 0, "Expected zero moves for full board")
    }

    func testGeneratesAllAvialable() {
        let generator = MoveGenerator(board: EmptyBoard())
        XCTAssertEqual(generator.forPosition((x: 0, y: 0)).count, 1, "Expected one move for empty board")
    }
}