Coding tests that show real skill.

1from typing import List
2
3def two_sum(nums: List[int], target: int) -> List[int]:
4    """Indices of the two numbers that add up to target."""
5    seen = {}
6    for i, x in enumerate(nums):
7        need = target - x
8        if need in seen:
9            return [seen[need], i]
10        seen[x] = i
11    return []
12
13
14def test_two_sum():
15    assert two_sum([2, 7, 11, 15], 9) == [0, 1]
16    assert two_sum([3, 2, 4], 6) == [1, 2]
17    assert two_sum([3, 3], 6) == [0, 1]