That is better, but doesn't check for incorrectly repeated elements:

    result = ["a", "b", "b"]
    assert set(result) == {"a", "b"}

In fact that is the first main motivating failure case discussed in the readme. But actually that's simple enough to deal with too:

    from collections import Counter
    assert Counter(result) = {"a": 1, "b": 1}

But would be trickier for mutable / unhashable types (not sure if "precisely" can deal with those).