from typing import List


def hasNoDuplicates(L: List[int]) -> bool:
    """Returns True if the list has no duplicates, False otherwise."""
    return len(set(L)) == len(L)


def testHasNoDuplicates():
    print("Testing hasNoDuplicates()...", end="")
    assert hasNoDuplicates([1, 2, 3, 2]) == False
    assert hasNoDuplicates([1, 2, 3, 4]) == True
    assert hasNoDuplicates([]) == True
    assert hasNoDuplicates([42]) == True
    assert hasNoDuplicates([42, 42]) == False

    # Verify that the function is nonmutating:
    L = [1, 2, 3, 2]
    hasNoDuplicates(L)
    assert L == [1, 2, 3, 2]
    print("Passed!")


def main():
    testHasNoDuplicates()


main()