diff --git a/src/main/c/GameTic_Tac_Toe/tictactoe.h b/src/main/c/GameTic_Tac_Toe/tictactoe.h
index a972d36..67f34cb 100644
--- a/src/main/c/GameTic_Tac_Toe/tictactoe.h
+++ b/src/main/c/GameTic_Tac_Toe/tictactoe.h
@@ -1,7 +1,9 @@
 #ifndef TICTACTOE_H
 #define TICTACTOE_H
 
+int isValidMove(int choice);
 char checkLine(char a, char b, char c);
 void start_tictactoe();
+char checkWinner();
 
 #endif
diff --git a/test/test_tictactoe.c b/test/test_tictactoe.c
index fb2e499..d7c864b 100644
--- a/test/test_tictactoe.c
+++ b/test/test_tictactoe.c
@@ -46,6 +46,7 @@ void test_checkLine_horizontalerGewinner(void) {
     TEST_ASSERT_EQUAL_CHAR('X', result);
 }
 
+
 void test_isValidMove_gueltigerZug(void) {
     /* arrangieren */
     int result;
@@ -57,4 +58,29 @@ void test_isValidMove_gueltigerZug(void) {
     /* überprüfen */
     TEST_ASSERT_EQUAL_INT(1, result);
 }
+
+
+void test_checkWinner_vertikalerGewinner(void) {
+    /* arrangieren */
+    char result;
+    
+    // Initialisiere das Spielfeld
+    for (int i = 0; i < BOARD_SIZE; i++) {
+        for (int j = 0; j < BOARD_SIZE; j++) {
+            board[i][j] = (char)('1' + i * BOARD_SIZE + j);
+        }
+    }
+
+    // Setze die Daten für einen vertikalen Gewinner
+    board[0][0] = 'O';
+    board[1][0] = 'O';
+    board[2][0] = 'O';
+
+    /* handeln */
+    result = checkWinner();
+
+    /* überprüfen */
+    TEST_ASSERT_EQUAL_CHAR('O', result);
+}
+
 #endif // TEST