Introduction to unit testing with Python (https://blog.tecladocode.com/introduction-to-unit-testing-with-python/) — final complete code

test_list_reversal.py

from unittest import TestCase
from typing import List

def has_mixed_types(list_: List):
    first = type(list_[0])
    return any(not isinstance(t, first) for t in list_)

def reverse_list(original: List) -> List:
    if has_mixed_types(original):
        raise ValueError("The list to be reversed should have homogeneous types.")
    return original[::-1]

class ReverseListTest(TestCase):
    def test_reverses_nonempty_list(self):
        original = [3, 7, 1, 10]
        expected = [10, 1, 7, 3]
        self.assertEqual(reverse_list(original), expected)

	def test_reverses_varying_elements_raises(self):
		original = [3, 7, "a"]
		with self.assertRaises(ValueError):
			reverse_list(original)
    
    def test_reverses_empty_list(self):
        original = []
        expected = []
        self.assertEqual(reverse_list(original), expected)
    
    def test_reversal_gives_new_list(self):
        original = [3, 5, 7]
        expected = [3, 5, 7]
        reverse_list(original)
        self.assertEqual(original, expected)
    
    def test_reversal_with_duplicates(self):
        original = [3, 4, 3, 3, 9]
        expected = [9, 3, 3, 4, 3]
        self.assertEqual(reverse_list(original), expected)