text: const { levelOrder, TreeNode } = require('./03')
  
  test('1', () => {
    const root = new TreeNode(3)
    const t1 = new TreeNode(9)
    const t2 = new TreeNode(20)
    const t3 = new TreeNode(15)
    const t4 = new TreeNode(7)
    root.left = t1
    root.right = t2
    t2.left = t3
    t2.right = t4
    expect(levelOrder(root)).toEqual([[3], [9, 20], [15, 7]])
  })
  
  test('2', () => {
    const root = new TreeNode(3)
    expect(levelOrder(root)).toEqual([[3]])
  })
  