Mimic challenge

main.py

from itertools import combinations


def permute(k, combo):
    if k == 1:
        yield combo
    else:
        for hp in permute(k - 1, combo):
            yield hp
        for i in range(0, k-1):
            j = 0 if (k % 2) == 1 else i
            combo[j], combo[k - 1] = combo[k - 1], combo[j]
            for hp in permute(k - 1, combo):
                yield hp


def sub_sets(word):
    return sum(list(list(combinations(word, n)) for n in range(1, len(word)+1)), [])


def main(word, permuter, sub_setter):
    for s in sub_setter(word):
        for permutation in permuter(len(s), list(s)):
            print(f" - {''.join(permutation)}")


def combos(word):
    main(word.upper(), permute, sub_sets)


if __name__ == '__main__':
    combos("abc")

test_main.py

from unittest import TestCase
from unittest.mock import MagicMock

from main import sub_sets, permute, main


class TestMain(TestCase):
    def setUp(self) -> None:
        self.sub_sets = sub_sets
        self.permute = permute
        self.main = main

    def test_sub_sets(self):
        self.assertEqual(self.sub_sets("AB"), [('A',), ('B',), ('A', 'B')])

    def test_permute(self):
        permutations = [i.copy() for i in self.permute(1, ["A"])]
        self.assertEqual(permutations, [["A"]])

        permutations = [i.copy() for i in self.permute(2, ["A", "B"])]
        self.assertEqual(permutations, [["A", "B"], ["B", "A"]])

    def test_main(self):
        permuter = MagicMock()
        sub_setter = MagicMock()

        sub_setter.return_value = ["A"]
        permuter.permutations = ["A"]

        self.assertIsNone(self.main("a", permuter, sub_setter))

        sub_setter.called_with("AB")