import unittest

#<!-- The Function the User needs to write -->
def revstring(x):
    return x[::-1]

#<!-- This Test, test if the function works -->
class TestSolution(unittest.TestCase):
    def test_simple(self):
        x = "Hello World"
        self.assertEqual(revstring(x), "dlroW olleH")  # Test simple string reversal
        self.assertEqual(revstring(""), "")  # Test empty string
        self.assertEqual(revstring("a"), "a")  # Test single character
        self.assertEqual(revstring("racecar"), "racecar")  # Test palindrome
        self.assertEqual(revstring("12345"), "54321")  # Test numbers as string
        self.assertEqual(revstring("!@# $%"), "%$ #@!")  # Test special chars and spaces

if __name__ == "__main__":
    unittest.main()