### Question:
RopeUtils { public static <T extends StreamElement> long characterCount(Node<T> x) { if (x == null) { return 0; } if (x.isLeaf()) { return x.value.getWidth(); } return x.weight + addWeightsOfRightLeaningChildNodes(x); }  static long addWeightsOfRightLeaningChildNodes(Node<T> x); static long addWeightsOfRightLeaningParentNodes(Node<T> child); static void adjustWeightOfLeftLeaningParents(Node<T> startNode, long weight); static long characterCount(Node<T> x); static void collectLeafNodes(Node<T> x, Queue<Node<T>> queue); static Node<T> concat(List<Node<T>> orphans); static Node<T> concat(Node<T> left, Node<T> right); static void cutLeftNode(Node<T> x, List<Node<T>> orphans); static void cutRightNode(Node<T> x, List<Node<T>> orphans); static Node<T> findRoot(Node<T> child); static Node<T> findSearchNode(Node<T> x, long weight, Node<T> root); static NodeIndex<T> index(long characterPosition, Node<T> x, long disp); static boolean intersects(long start, long end, long start2, long end2); static Node<T> rebalance(Node<T> x);  }### Answer:
@Test public void characterCount() throws Exception { Node<InvariantSpan> right = new Node<>(new InvariantSpan(1, 10, documentHash)); Node<InvariantSpan> right2 = new Node<>(new InvariantSpan(1, 20, documentHash)); right.right = right2; Node<InvariantSpan> x = new Node.Builder<InvariantSpan>(10).right(right).build(); assertEquals(40, RopeUtils.characterCount(x)); }
@Test public void characterCountLeafNode() throws Exception { assertEquals(3, RopeUtils.characterCount(new Node<>(new InvariantSpan(1, 3, documentHash)))); }
@Test public void characterCountNullNode() throws Exception { assertEquals(0, RopeUtils.characterCount(null)); }