diff --git a/solutions/tests/test_sum_proper_divisors.py b/solutions/tests/test_sum_proper_divisors.py
index 566bb2c59..f09952bb2 100644
--- a/solutions/tests/test_sum_proper_divisors.py
+++ b/solutions/tests/test_sum_proper_divisors.py
@@ -1,3 +1,11 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Unit tests for the sum_proper_divisors function.
+
+This module contains unit tests for the sum_proper_divisors function.
+"""
+
 import unittest
 
 from ..sum_proper_divisors import sum_proper_divisors