@Test
public void testFirst() {

  FoldedTreeSet<Integer> tree = new FoldedTreeSet<>();
  for (int i = 0; i < 256; i++) {
    tree.add(1024 + i);
    assertEquals(1024, tree.first().intValue());
  }
  for (int i = 1; i < 256; i++) {
    tree.remove(1024 + i);
    assertEquals(1024, tree.first().intValue());
  }
}