Quicksort in Python

quicksort.py

import unittest
from hypothesis import given
from hypothesis import strategies as st


def quicksort(numbers):
    if len(numbers) == 0:
        return numbers
    else:
        first = numbers[0]
        remaining = numbers[1:]
        sorted_remaining = quicksort(remaining)

        less_than = [number for number in sorted_remaining if number <= first]
        greater_than = [number for number in sorted_remaining if number > first]
        return less_than + [first] + greater_than


class TestSort(unittest.TestCase):

    def test_empty(self):
        self.assertEqual(quicksort([]), [])

    def test_sorted(self):
        self.assertEqual(quicksort([1,2,3]), [1,2,3])

    def test_unsorted(self):
        self.assertEqual(quicksort([1,4,3,2]), [1,2,3,4])

    @given(numbers=st.lists(st.integers()))
    def test_same_length(self, numbers):
        self.assertEqual(len(quicksort(numbers)), len(numbers))


if __name__ == '__main__':
    unittest.main()