diff --git a/bit_manipulation/binary_count_trailing_zeros.py b/bit_manipulation/binary_count_trailing_zeros.py
index f401c4ab9266..751f36720fa2 100644
--- a/bit_manipulation/binary_count_trailing_zeros.py
+++ b/bit_manipulation/binary_count_trailing_zeros.py
@@ -17,7 +17,9 @@ def binary_count_trailing_zeros(a: int) -> int:
     >>> binary_count_trailing_zeros(4294967296)
     32
     >>> binary_count_trailing_zeros(0)
-    0
+    Traceback (most recent call last):
+        ...
+    ValueError: Input value must be a positive integer
     >>> binary_count_trailing_zeros(-10)
     Traceback (most recent call last):
         ...
@@ -31,11 +33,11 @@ def binary_count_trailing_zeros(a: int) -> int:
         ...
     TypeError: '<' not supported between instances of 'str' and 'int'
     """
-    if a < 0:
-        raise ValueError("Input value must be a positive integer")
-    elif isinstance(a, float):
+    if isinstance(a, float):
         raise TypeError("Input value must be a 'int' type")
-    return 0 if (a == 0) else int(log2(a & -a))
+    if a < 0 or a == 0:
+        raise ValueError("Input value must be a positive integer")
+    return int(log2(a & -a))
 
 
 if __name__ == "__main__":
diff --git a/ciphers/a1z26.py b/ciphers/a1z26.py
index a1377ea6d397..102cef4e424e 100644
--- a/ciphers/a1z26.py
+++ b/ciphers/a1z26.py
@@ -13,7 +13,13 @@ def encode(plain: str) -> list[int]:
     """
     >>> encode("myname")
     [13, 25, 14, 1, 13, 5]
+    >>> encode("ABCD")
+    Traceback (most recent call last):
+        ...
+    ValueError: plain must contain only lowercase letters (a-z)
     """
+    if not plain.islower() or not plain.isalpha():
+        raise ValueError("plain must contain only lowercase letters (a-z)")
     return [ord(elem) - 96 for elem in plain]
 
 
diff --git a/sorts/insertion_sort.py b/sorts/insertion_sort.py
index 2e39be255df7..24f53b654439 100644
--- a/sorts/insertion_sort.py
+++ b/sorts/insertion_sort.py
@@ -31,6 +31,16 @@ def insertion_sort[T: Comparable](collection: MutableSequence[T]) -> MutableSequ
     comparable items inside
     :return: the same collection ordered by ascending
 
+    Complexity Analysis:
+        Time Complexity:
+            - Best Case: O(n) when the collection is already sorted
+            - Average Case: O(n^2)
+            - Worst Case: O(n^2) when the collection is sorted in reverse order
+
+        Space Complexity:
+            - O(1) because the algorithm sorts the collection in place and
+              uses only a constant amount of additional memory
+
     Examples:
     >>> insertion_sort([0, 5, 3, 2, 2])
     [0, 2, 2, 3, 5]