public void IntersectUniverse()
{
Assert.AreEqual(LongSet.Universe, LongSet.Universe.IntersectWith(LongSet.Universe));
Assert.AreEqual(LongSet.Empty, LongSet.Universe.IntersectWith(LongSet.Empty));
Assert.AreEqual(new LongSet(long.MaxValue), LongSet.Universe.IntersectWith(new LongSet(long.MaxValue)));
var longSet = new LongSet(new[] { new LongInterval(1, 5), new LongInterval(6, 7) }.ToImmutableArray());
Assert.AreEqual(longSet, longSet.IntersectWith(LongSet.Universe));
}