Added test for different input in input handler

test/test_inputHandler.c

@@ -15,4 +15,11 @@ void test_inputHandler_returntwoforinputminus(void) {
     int result;
     result = getOperationIdBySymbol('-');
     TEST_ASSERT_EQUAL_INT(expectedResult, result);
-}
+}
+
+void test_inputHandler_returnoneforinputplus(void) {
+    int expectedResult = 1;
+    int result;
+    result = getOperationIdBySymbol('+');
+    TEST_ASSERT_EQUAL_INT(expectedResult, result);
+}