@Test
  public void testDifference() {
    int maxsize = 16;
    mts = new MerkleTrees(partitioner);
    mts.addMerkleTree(32, fullRange());

    MerkleTrees mts2 = new MerkleTrees(partitioner);
    mts2.addMerkleTree(32, fullRange());

    mts.init();
    mts2.init();

    // add dummy hashes to both trees
    for (TreeRange range : mts.invalids()) range.addAll(new HIterator(range.right));
    for (TreeRange range : mts2.invalids()) range.addAll(new HIterator(range.right));

    TreeRange leftmost = null;
    TreeRange middle = null;

    mts.maxsize(fullRange(), maxsize + 2); // give some room for splitting

    // split the leftmost
    Iterator<TreeRange> ranges = mts.invalids();
    leftmost = ranges.next();
    mts.split(leftmost.right);

    // set the hashes for the leaf of the created split
    middle = mts.get(leftmost.right);
    middle.hash("arbitrary!".getBytes());
    mts.get(partitioner.midpoint(leftmost.left, leftmost.right))
        .hash("even more arbitrary!".getBytes());

    // trees should disagree for (leftmost.left, middle.right]
    List<Range<Token>> diffs = MerkleTrees.difference(mts, mts2);
    assertEquals(diffs + " contains wrong number of differences:", 1, diffs.size());
    assertTrue(diffs.contains(new Range<>(leftmost.left, middle.right)));
  }
 private Range<Token> fullRange() {
   return new Range<>(partitioner.getMinimumToken(), partitioner.getMinimumToken());
 }