let test = xs => {
assert.deepEqual([...dropWhile(isNegative, xs)],
[0, 1, 2],
"dropped negative");
assert.deepEqual([...dropWhile(True, xs)],
[],
"drop all");
assert.deepEqual([...dropWhile(False, xs)],
[-2, -1, 0, 1, 2],
"keep all");
};
assert.throws(() => [...dropWhile(x => true, broken)],
assert.throws(() => [...dropWhile(boom, [1, 2, 3])],