text: import unittest
  
  from satellite import (
      tree_from_traversals,
  )
  
  # Tests adapted from `problem-specifications//canonical-data.json`
  
  
  class SatelliteTest(unittest.TestCase):
      def test_empty_tree(self):
          preorder = []
          inorder = []
  
          expected = {}
          self.assertEqual(tree_from_traversals(preorder, inorder), expected)
  
      def test_tree_with_one_item(self):
          preorder = ["a"]
          inorder = ["a"]
  
          expected = {"v": "a", "l": {}, "r": {}}
          self.assertEqual(tree_from_traversals(preorder, inorder), expected)
  
      def test_tree_with_many_items(self):
          preorder = ["a", "i", "x", "f", "r"]
          inorder = ["i", "a", "f", "x", "r"]
  
          expected = {
              "v": "a",
              "l": {"v": "i", "l": {}, "r": {}},
              "r": {
                  "v": "x",
                  "l": {"v": "f", "l": {}, "r": {}},
                  "r": {"v": "r", "l": {}, "r": {}},
              },
          }
          self.assertEqual(tree_from_traversals(preorder, inorder), expected)
  
      def test_reject_traversals_of_different_length(self):
          preorder = ["a", "b"]
          inorder = ["b", "a", "r"]
  
          with self.assertRaises(ValueError) as err:
              tree_from_traversals(preorder, inorder)
          self.assertEqual(type(err.exception), ValueError)
          self.assertEqual(err.exception.args[0], "traversals must have the same length")
  
      def test_reject_inconsistent_traversals_of_same_length(self):
          preorder = ["x", "y", "z"]
          inorder = ["a", "b", "c"]
  
          with self.assertRaises(ValueError) as err:
              tree_from_traversals(preorder, inorder)
          self.assertEqual(type(err.exception), ValueError)
          self.assertEqual(
              err.exception.args[0], "traversals must have the same elements"
          )
  
      def test_reject_traversals_with_repeated_items(self):
          preorder = ["a", "b", "a"]
          inorder = ["b", "a", "a"]
  
          with self.assertRaises(ValueError) as err:
              tree_from_traversals(preorder, inorder)
          self.assertEqual(type(err.exception), ValueError)
          self.assertEqual(err.exception.args[0], "traversals must contain unique items")
  