Add tests for reverse_string and improve string reversal logic

string_reversal.py

@@ -0,0 +1,27 @@
+def reverse_string(s):
+    """Reverses a string.
+
+    Args:
+      s: A string.
+
+    Returns:
+      A string containing the reversed characters of s.
+    """
+    if not isinstance(s, str):
+        raise TypeError("Input must be a string.")
+    return s[::-1]
+
+
+def main():
+    """Reverses the string 'Hello, world!' and prints it to the console."""
+
+    input_string = "Hello, world!"
+    reversed_string = reverse_string(input_string)
+    print(f"Reversed string: {reversed_string}")
+
+
+if __name__ == "__main__":
+    main()
+
+"""Output:
+Reversed string: !dlrow ,olleH"""

tests/test_string_reversal.py

@@ -0,0 +1,33 @@
+import pytest
+from string_reversal import reverse_string
+
+
+def test_basic_reversal():
+    assert reverse_string("hello") == "olleh"
+    assert reverse_string("Python") == "nohtyP"
+
+
+def test_empty_string():
+    assert reverse_string("") == ""
+
+
+def test_palindrome():
+    s = "madam"
+    assert reverse_string(s) == s
+
+
+def test_whitespace_and_symbols():
+    assert reverse_string("  abc ") == " cba  "
+    assert reverse_string("123!@#") == "#@!321"
+
+
+def test_unicode_characters():
+    assert reverse_string("äöü") == "üöä"
+    assert reverse_string("你好") == "好你"
+
+
+def test_non_string_input():
+    with pytest.raises(TypeError):
+        reverse_string(123)
+    with pytest.raises(TypeError):
+        reverse_string(None)