diff --git a/src/__pycache__/string_utils.cpython-312.pyc b/src/__pycache__/string_utils.cpython-312.pyc
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diff --git a/src/string_utils.py b/src/string_utils.py
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+def reverse_string(input_string):
+    """
+    Reverse a given string using manual character iteration.
+
+    Args:
+        input_string (str): The string to be reversed.
+
+    Returns:
+        str: The reversed string.
+
+    Raises:
+        TypeError: If the input is not a string.
+    """
+    # Check if input is a string
+    if not isinstance(input_string, str):
+        raise TypeError("Input must be a string")
+    
+    # Manual string reversal
+    reversed_str = ""
+    for char in input_string:
+        reversed_str = char + reversed_str
+    
+    return reversed_str
+
+def rgb_to_hex(r, g, b):
+    """
+    Convert RGB color values to a hexadecimal color code.
+
+    Args:
+        r (int): Red color value (0-255)
+        g (int): Green color value (0-255)
+        b (int): Blue color value (0-255)
+
+    Returns:
+        str: Hexadecimal color code (e.g., '#FF0000' for bright red)
+
+    Raises:
+        ValueError: If any color value is outside the range 0-255
+        TypeError: If any input is not an integer
+    """
+    # Validate input types
+    if not all(isinstance(x, int) for x in (r, g, b)):
+        raise TypeError("RGB values must be integers")
+    
+    # Validate color values are within 0-255 range
+    if not all(0 <= x <= 255 for x in (r, g, b)):
+        raise ValueError("RGB values must be between 0 and 255")
+    
+    # Convert to hex, ensuring two-digit representation
+    hex_color = '#{:02X}{:02X}{:02X}'.format(r, g, b)
+    
+    return hex_color
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diff --git a/tests/__pycache__/test_string_utils.cpython-312-pytest-8.3.5.pyc b/tests/__pycache__/test_string_utils.cpython-312-pytest-8.3.5.pyc
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diff --git a/tests/test_string_utils.py b/tests/test_string_utils.py
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+import pytest
+from src.string_utils import rgb_to_hex, reverse_string
+
+def test_reverse_string():
+    assert reverse_string("hello") == "olleh"
+    assert reverse_string("") == ""
+    assert reverse_string("a") == "a"
+    with pytest.raises(TypeError):
+        reverse_string(123)
+
+def test_rgb_to_hex_basic_conversion():
+    """Test basic RGB to hex conversion"""
+    assert rgb_to_hex(255, 0, 0) == '#FF0000'  # Bright Red
+    assert rgb_to_hex(0, 255, 0) == '#00FF00'  # Bright Green
+    assert rgb_to_hex(0, 0, 255) == '#0000FF'  # Bright Blue
+    assert rgb_to_hex(0, 0, 0) == '#000000'   # Black
+    assert rgb_to_hex(255, 255, 255) == '#FFFFFF'  # White
+
+def test_rgb_to_hex_mixed_colors():
+    """Test conversion of mixed color values"""
+    assert rgb_to_hex(128, 128, 128) == '#808080'  # Mid Gray
+    assert rgb_to_hex(100, 200, 50) == '#64C832'  # Mixed color
+
+def test_rgb_to_hex_type_errors():
+    """Test type validation for inputs"""
+    with pytest.raises(TypeError):
+        rgb_to_hex('255', 0, 0)
+    with pytest.raises(TypeError):
+        rgb_to_hex(255, '0', 0)
+    with pytest.raises(TypeError):
+        rgb_to_hex(255, 0, '0')
+    with pytest.raises(TypeError):
+        rgb_to_hex(255.5, 0, 0)
+
+def test_rgb_to_hex_value_errors():
+    """Test value range validation"""
+    with pytest.raises(ValueError):
+        rgb_to_hex(-1, 0, 0)
+    with pytest.raises(ValueError):
+        rgb_to_hex(0, 256, 0)
+    with pytest.raises(ValueError):
+        rgb_to_hex(0, 0, 300)
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