fix: use negative number for testing exception

Author: dhruvmanila

maths/prime_check.py

@@ -63,7 +63,7 @@ def test_primes(self):
 
     def test_not_primes(self):
         with self.assertRaises(AssertionError):
-            is_prime(19)
+            is_prime(-19)
         self.assertFalse(
             is_prime(0),
             "Zero doesn't have any positive factors, primes must have exactly two.",