tictactoe: countCharsInDiag counts number of given char in specific diagonal

src/main/java/de/tims/tictactoe/ai/AIHard.java

@@ -79,6 +79,13 @@ public class AIHard implements TicTacToeAI {
 	}
 	
 	public int countCharsInDiag(int index, char charToCount) {
-		return 0;
+		int count = 0;
+		char[][] board = gl.getBoard();
+		
+		for (int i = 0; i < BOARD_SIZE; i++) {
+			count += (board[i][(index == 0) ? i : BOARD_SIZE - 1 - i] == charToCount) ? 1 : 0;
+		}
+		
+		return count;
 	}
 }

src/test/java/de/tims/tictactoe/ai/AIHardTest.java

@@ -120,7 +120,10 @@ class AIHardTest {
 	private static Stream<Arguments> testCasesForCountCharsInDiag() {
 		return Stream.of(Arguments.of("EmptyFieldReturns0", 
 						new char[][] { {'-', '-', '-'}, {'-', '-', '-'}, {'-', '-', '-'} },
-						0, 'o', 0));
+						0, 'o', 0),
+				Arguments.of("TwoCharsInRowReturnsTwo", 
+						new char[][] { {'-', '-', 'o'}, {'o', 'o', '-'}, {'-', '-', '-'} },
+						1, 'o', 2));
 	}
 
 }