Enhance String Reversal Utility with Robust Implementation and Comprehensive Testing

src/string_reversal.py

@@ -1,4 +1,4 @@
-def reverse_string(input_string):
+def reverse_string(input_string: str) -> str:
     """
     Reverse the given input string manually, without using slice notation or reverse().
 
@@ -15,10 +15,14 @@ def reverse_string(input_string):
     if not isinstance(input_string, str):
         raise TypeError("Input must be a string")
 
-    # Convert string to list of characters
+    # Handle empty string case
+    if not input_string:
+        return ""
+
+    # Convert string to list of characters for manipulation
     chars = list(input_string)
 
-    # Manually reverse the list of characters
+    # Reverse the list using two-pointer technique
     left, right = 0, len(chars) - 1
     while left < right:
         # Swap characters from both ends

src/string_utils.py

@@ -11,14 +11,12 @@ def reverse_string(input_string):
     Raises:
         TypeError: If the input is not a string.
     """
-    # Type checking
+    # Enhanced type checking with more explicit validation
     if not isinstance(input_string, str):
         raise TypeError("Input must be a string")
 
-    # Use list to manually reverse the string
-    reversed_chars = []
-    for i in range(len(input_string) - 1, -1, -1):
-        reversed_chars.append(input_string[i])
+    # Efficient string reversal using list comprehension
+    reversed_chars = [input_string[i] for i in range(len(input_string) - 1, -1, -1)]
 
     # Convert list back to string
     return ''.join(reversed_chars)

tests/test_string_reversal.py

@@ -9,29 +9,32 @@ def test_reverse_empty_string():
     """Test reversing an empty string."""
     assert reverse_string("") == ""
 
+def test_reverse_single_char_string():
+    """Test reversing a single character string."""
+    assert reverse_string("a") == "a"
+
 def test_reverse_palindrome():
-    """Test reversing a palindrome string."""
+    """Test reversing a palindrome."""
     assert reverse_string("racecar") == "racecar"
 
 def test_reverse_with_spaces():
     """Test reversing a string with spaces."""
     assert reverse_string("hello world") == "dlrow olleh"
 
-def test_reverse_with_special_characters():
+def test_reverse_with_special_chars():
     """Test reversing a string with special characters."""
+    assert reverse_string("hello!@#") == "#@!olleh"
     assert reverse_string("a1b2c3!@#") == "#@!3c2b1a"
 
 def test_reverse_unicode_string():
-    """Test reversing a string with Unicode characters."""
+    """Test reversing a Unicode string."""
     assert reverse_string("こんにちは") == "はちにんこ"
 
 def test_invalid_input_type():
-    """Test that a TypeError is raised for non-string inputs."""
+    """Test raising TypeError for non-string input."""
     with pytest.raises(TypeError, match="Input must be a string"):
-        reverse_string(12345)
-
+        reverse_string(123)
     with pytest.raises(TypeError, match="Input must be a string"):
         reverse_string(None)
-
     with pytest.raises(TypeError, match="Input must be a string"):
         reverse_string(["hello"])