carmichael_number - add doctests

maths/carmichael_number.py

@@ -10,17 +10,20 @@
 Examples of Carmichael Numbers: 561, 1105, ...
 https://en.wikipedia.org/wiki/Carmichael_number
 """
+from maths.greatest_common_divisor import greatest_common_divisor
 
 
-def gcd(a: int, b: int) -> int:
-    if a < b:
-        return gcd(b, a)
-    if a % b == 0:
-        return b
-    return gcd(b, a % b)
+def power(x: int, y: int, mod: int) -> int:
+    """
 
+    Examples:
+    >>> power(2, 15, 3)
+    2
+
+    >>> power(5, 1, 30)
+    5
+    """
 
-def power(x: int, y: int, mod: int) -> int:
     if y == 0:
         return 1
     temp = power(x, y // 2, mod) % mod
@@ -31,15 +34,38 @@ def power(x: int, y: int, mod: int) -> int:
 
 
 def is_carmichael_number(n: int) -> bool:
+    """
+
+    Examples:
+    >>> is_carmichael_number(562)
+    False
+
+    >>> is_carmichael_number(561)
+    True
+
+    >>> is_carmichael_number(5.1)
+    Traceback (most recent call last):
+         ...
+    ValueError: Number 5.1 must instead be integer
+    """
+
+    if not isinstance(n, int):
+        msg = f"Number {n} must instead be integer"
+        raise ValueError(msg)
+
     b = 2
     while b < n:
-        if gcd(b, n) == 1 and power(b, n - 1, n) != 1:
+        if greatest_common_divisor(b, n) == 1 and power(b, n - 1, n) != 1:
             return False
         b += 1
     return True
 
 
 if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+
     number = int(input("Enter number: ").strip())
     if is_carmichael_number(number):
         print(f"{number} is a Carmichael Number.")