Added changes as per request of the reveiwer such as including edge c…

…ases tests and more descriptive docstrings

solutions/Swap_letters.py

@@ -2,6 +2,8 @@
 Created on 08/01/2024
 
 @author: Tibyan Khalid
+
+This file contains the function Swap_letters that swaps the case of each letter in a string.
 """
 
 
@@ -29,9 +31,9 @@ def Swap_letters(string: str) -> str:
     changed_string = ""
     for char in string:
         if char.islower():
-            changed_string = changed_string + char.upper()
+            changed_string += char.upper()
         elif char.isupper():
-            changed_string = changed_string + char.lower()
+            changed_string += char.lower()
         else:
-            changed_string = changed_string + char
+            changed_string += char
     return changed_string

solutions/tests/test_Swap_letters.py

@@ -2,15 +2,18 @@
 Created on 08/01/2024
 
 @author: Tibyan Khalid
+
+This file contains boundary cases and defensive assertion tests for the function Swap_letters.
 """
 
 import unittest
 
 from ..Swap_letters import Swap_letters
 
 
-class TestSwapletters(unittest.TestCase):
-    """Unittests for the Swap_letters function"""
+class TestSwapLettersFunctionality(unittest.TestCase):
+    """Test cases for validating the behavior of the Swap_letters function,
+    including edge cases and defensive assertions."""
 
     def test_lowercase_all(self):
         "Testing from lowercase to uppercase"
@@ -33,6 +36,14 @@ def test_spaces(self):
         "Handle spaces correctly"
         self.assertEqual(Swap_letters("Hello World"), "hELLO wORLD")
 
+    def test_empty_string(self):
+        "Test for an empty string input"
+        self.assertEqual(Swap_letters(""), "")
+
+    def test_special_characters(self):
+        "Test for special characters input"
+        self.assertEqual(Swap_letters("1234!@#$"), "1234!@#$")
+
 
 if __name__ == "__main__":
     unittest.main()