Robust String Reversal Implementation with Comprehensive Test Coverage

src/string_reversal.py

@@ -0,0 +1,37 @@
+def reverse_string(s: str) -> str:
+    """
+    Reverse the given string using a manual character-by-character approach.
+
+    Args:
+        s (str): The input string to be reversed.
+
+    Returns:
+        str: The reversed string.
+
+    Raises:
+        TypeError: If the input is not a string.
+    """
+    # Type checking
+    if not isinstance(s, str):
+        raise TypeError("Input must be a string")
+
+    # Handle empty string case
+    if len(s) <= 1:
+        return s
+
+    # Manual string reversal
+    # Convert string to list of characters for easy manipulation
+    chars = list(s)
+
+    # Two-pointer approach to swap characters
+    left, right = 0, len(chars) - 1
+    while left < right:
+        # Swap characters
+        chars[left], chars[right] = chars[right], chars[left]
+
+        # Move pointers
+        left += 1
+        right -= 1
+
+    # Convert list back to string and return
+    return ''.join(chars)

tests/test_string_reversal.py

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+import pytest
+from src.string_reversal import reverse_string
+
+def test_reverse_string_basic():
+    """Test basic string reversal."""
+    assert reverse_string("hello") == "olleh"
+    assert reverse_string("world") == "dlrow"
+
+def test_reverse_string_empty():
+    """Test reversing an empty string."""
+    assert reverse_string("") == ""
+
+def test_reverse_string_single_char():
+    """Test reversing a single character string."""
+    assert reverse_string("a") == "a"
+
+def test_reverse_string_with_spaces():
+    """Test reversing a string with spaces."""
+    assert reverse_string("hello world") == "dlrow olleh"
+
+def test_reverse_string_with_special_chars():
+    """Test reversing a string with special characters."""
+    assert reverse_string("a1b2c3!@#") == "#@!3c2b1a"
+
+def test_reverse_string_with_mixed_chars():
+    """Test reversing a string with mixed characters."""
+    assert reverse_string("Hello, World! 123") == "321 !dlroW ,olleH"
+
+def test_reverse_string_invalid_input():
+    """Test that TypeError is raised for non-string inputs."""
+    with pytest.raises(TypeError, match="Input must be a string"):
+        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(["list"])