function verifyNode(node: ITreeNode, path: string[]) {
   expect(node.id).toEqual(path[0]);
   expect(node.text).toEqual(path[0]);
   if (path.length === 1) {
     expect(node.children === null || node.children.length === 0);
   } else {
     expect(node.children.length).toBe(1);
     verifyNode(node.children[0], R.drop(1, path));
   }
 }

    public static sort(unsorted: number [] = []): number[] {

        if (unsorted.length !== 0) {
            const sorted = [];
            const m = R.head(unsorted);

            const {l, h} = R.groupBy(curr => R.gte(curr, m) ? 'h' : 'l', R.drop(1, unsorted))

            sorted.push(...QuickSort.sort(l));
            sorted.push(m);
            sorted.push(...QuickSort.sort(h));
            return sorted;
        } else
            return unsorted;
    }

export const pinNumbers = (observed: string): Array<String> => {
  const lookUp = ['08', '124', '1235', '236', '1457', '24568', '3569', '478', '57890', '689'];

  let obsHead: string = head(observed);

  const heads = lookUp[obsHead];

  if (observed.length <= 1)
    return split('', heads);

  const result = [];
  for (const h of heads) {
    for (const t of pinNumbers(drop(1, observed))) {
      result.push(h + t)
    }
  }
  return result
};

 [isStrike, rolls => add(add(nth(1, rolls), nth(2, rolls)), bonus(drop(1, rolls)))],

 [T, rolls => bonus(drop(2, rolls))],

 [isSpare, rolls => nth(2, rolls) + bonus(drop(2, rolls))],