def problem14():
""" Longest Collatz sequence
Which starting number, under one million, produces the longest chain?
"""
longest_chain = 1
chain_number = 1
for number in range(1, 1000000):
chain_count = mathhelper.collatz_sequence_chain_count(number)
if chain_count > longest_chain:
longest_chain = chain_count
chain_number = number
return chain_number
def test_collatz_sequence_chain_count(self):
self.assertEqual(mathhelper.collatz_sequence_chain_count(1), 1)
self.assertEqual(mathhelper.collatz_sequence_chain_count(2), 2)
self.assertEqual(mathhelper.collatz_sequence_chain_count(3), 8)
self.assertEqual(mathhelper.collatz_sequence_chain_count(13), 10)
