tictactoe: added test case for trying to set a field again

src/main/java/de/tims/tictactoe/GameLogic.java

@@ -5,7 +5,7 @@ import java.util.Arrays;
 public class GameLogic {
 	
 	private char[][] board;
-	private final char emptyField = '-';
+	private final char[] occupiedFields = { 'x', 'o' };
 
 	public GameLogic(int size) {
 		if (size < 3) {
@@ -33,11 +33,14 @@ public class GameLogic {
 	}
 
 	public void setField(int column, int row, char player) {
-			this.board[column][row] = player;
+		if(fieldIsEmpty(column, row)) this.board[column][row] = player;
 	}
 
 	public boolean fieldIsEmpty(int column, int row) {
-		return (this.board[column][row] == emptyField) ? true : false;
+		for (char field : this.occupiedFields) {
+			if (this.board[column][row] == field) return false;
+		}
+		return true;
 	}
 
 }

src/test/java/de/tims/tictactoe/GameLogicTest.java

@@ -86,6 +86,10 @@ class GameLogicTest {
 								    											  {'-', '-', '-'},
 								    											  {'-', '-', '-'}}),
 					    Arguments.of("set field [1][0] for player 2", 1, 0, 'o', new char[][] 
+																				 {{'x', '-', '-'}, 
+																				  {'o', '-', '-'},
+																				  {'-', '-', '-'}}),
+					    Arguments.of("try to set occupied field [1][0] for player 1", 1, 0, 'x', new char[][] 
 																								 {{'x', '-', '-'}, 
 																								  {'o', '-', '-'},
 																								  {'-', '-', '-'}})