Quick demo running pytest, hypothesis, and doctest together

pytest.ini

[pytest]
addopts = --doctest-modules

test_tidy.py

import hypothesis
from hypothesis.strategies import integers
import pytest

from tidy import max_tidy, tidy

def test_max_tidy():
    """simple pytest"""
    assert max_tidy(9) == 9

@pytest.mark.parametrize("test_input,expected", [
    (132, 129),
    (1000, 999),
    (1111111111111111110, 999999999999999999),
])
def test_max_tidy_cases(test_input, expected):
    """pytest parameterization"""
    assert max_tidy(test_input) == expected

@hypothesis.given(integers(min_value=1))
def test_max_tidy_props(n):
    """hypothesis givens"""
    t = max_tidy(n)
    assert t <= n
    assert tidy(t)

tidy.py

import sys


def tidy(n):
    """Test if n is tidy.

    A tidy number is a positive integer with nondecreasing digits as read from
    left to right.

    Any one digit number is tidy.
    >>> tidy(1)
    True
    >>> tidy(9)
    True

    A number with decreasing digits is not tidy.
    >>> tidy(21)
    False

    A number with repeated digits is ok, though.
    >>> tidy(112233)
    True
    """

    if n < 1:
        return False

    chars = list(str(n))
    for i in range(1, len(chars)):
        if chars[i] < chars[i-1]:
            return False

    return True

def max_tidy(n):
    """Find the largest tidy number <= n
    """
    chars = list(str(n))

    while True:
        for i in range(1, len(chars)):
            if chars[i] >= chars[i-1]:
                continue
            else:
                split = i
                break
        else:
            return int(''.join(chars))

        left = list(str(int(''.join(chars[:split])) - 1))
        right = ['9'] * len(chars[split:])
        chars = left+right

def main():
    t = int(sys.stdin.readline())   

    for case in range(1, t+1):
        n = int(sys.stdin.readline())
        print("Case #{}: {}".format(case, max_tidy(n)))
        

if __name__ == "__main__":
    main()