diff --git a/src/TicTacToe.h b/src/TicTacToe.h
index 64933e5..d7a57e0 100644
--- a/src/TicTacToe.h
+++ b/src/TicTacToe.h
@@ -1,4 +1,6 @@
 #ifndef TICTACTOE_H
 #define TICTACTOE_H
 
+int switchPlayer(int currentPlayer);
+
 #endif // TICTACTOE_H
\ No newline at end of file
diff --git a/test/test_tictactoe.c b/test/test_tictactoe.c
new file mode 100644
index 0000000..17dc2a5
--- /dev/null
+++ b/test/test_tictactoe.c
@@ -0,0 +1,19 @@
+#ifdef TEST
+
+#include "unity.h"
+
+#include "TicTacToe.h"
+
+void setUp(void)
+{
+}
+
+void tearDown(void)
+{
+}
+
+void test_switchPlayer_10_to_11(void) {
+    TEST_ASSERT(switchPlayer(10) == 11);
+}
+
+#endif // TEST
\ No newline at end of file