add move preconditions

app/src/main/java/chess/io/commands/CastlingCommand.java

@@ -4,10 +4,14 @@ import chess.io.OutputSystem;
 import chess.io.PlayerCommand;
 import chess.model.Game;
 
-public class CastlingCommand extends PlayerCommand{
+public class CastlingCommand extends PlayerCommand {
 
 	@Override
 	public CommandResult execute(Game game, OutputSystem outputSystem) {
+		// we must promote the pending pawn before
+		if (game.pawnShouldBePromoted())
+			return CommandResult.NotAllowed;
+
 		return CommandResult.NotAllowed;
 	}
 
@@ -16,5 +20,5 @@ public class CastlingCommand extends PlayerCommand{
 		// TODO Auto-generated method stub
 		throw new UnsupportedOperationException("Unimplemented method 'undo'");
 	}
-	
+
 }

app/src/main/java/chess/io/commands/GrandCastlingCommand.java

@@ -8,6 +8,10 @@ public class GrandCastlingCommand extends PlayerCommand {
 
 	@Override
 	public CommandResult execute(Game game, OutputSystem outputSystem) {
+		// we must promote the pending pawn before
+		if (game.pawnShouldBePromoted())
+			return CommandResult.NotAllowed;
+
 		return CommandResult.NotAllowed;
 	}