code: import numpy as np
  import pytest
  
  from pandas import Categorical, CategoricalIndex, DataFrame, Index, Series
  import pandas._testing as tm
  
  
  class TestReindex:
      def test_reindex_dtype(self):
          c = CategoricalIndex(["a", "b", "c", "a"])
          res, indexer = c.reindex(["a", "c"])
          tm.assert_index_equal(res, Index(["a", "a", "c"]), exact=True)
          tm.assert_numpy_array_equal(indexer, np.array([0, 3, 2], dtype=np.intp))
  
          c = CategoricalIndex(["a", "b", "c", "a"])
          res, indexer = c.reindex(Categorical(["a", "c"]))
  
          exp = CategoricalIndex(["a", "a", "c"], categories=["a", "c"])
          tm.assert_index_equal(res, exp, exact=True)
          tm.assert_numpy_array_equal(indexer, np.array([0, 3, 2], dtype=np.intp))
  
          c = CategoricalIndex(["a", "b", "c", "a"], categories=["a", "b", "c", "d"])
          res, indexer = c.reindex(["a", "c"])
          exp = Index(["a", "a", "c"], dtype="object")
          tm.assert_index_equal(res, exp, exact=True)
          tm.assert_numpy_array_equal(indexer, np.array([0, 3, 2], dtype=np.intp))
  
          c = CategoricalIndex(["a", "b", "c", "a"], categories=["a", "b", "c", "d"])
          res, indexer = c.reindex(Categorical(["a", "c"]))
          exp = CategoricalIndex(["a", "a", "c"], categories=["a", "c"])
          tm.assert_index_equal(res, exp, exact=True)
          tm.assert_numpy_array_equal(indexer, np.array([0, 3, 2], dtype=np.intp))
  
      def test_reindex_duplicate_target(self):
          # See GH25459
          cat = CategoricalIndex(["a", "b", "c"], categories=["a", "b", "c", "d"])
          res, indexer = cat.reindex(["a", "c", "c"])
          exp = Index(["a", "c", "c"], dtype="object")
          tm.assert_index_equal(res, exp, exact=True)
          tm.assert_numpy_array_equal(indexer, np.array([0, 2, 2], dtype=np.intp))
  
          res, indexer = cat.reindex(
              CategoricalIndex(["a", "c", "c"], categories=["a", "b", "c", "d"])
          )
          exp = CategoricalIndex(["a", "c", "c"], categories=["a", "b", "c", "d"])
          tm.assert_index_equal(res, exp, exact=True)
          tm.assert_numpy_array_equal(indexer, np.array([0, 2, 2], dtype=np.intp))
  
      def test_reindex_empty_index(self):
          # See GH16770
          c = CategoricalIndex([])
          res, indexer = c.reindex(["a", "b"])
          tm.assert_index_equal(res, Index(["a", "b"]), exact=True)
          tm.assert_numpy_array_equal(indexer, np.array([-1, -1], dtype=np.intp))
  
      def test_reindex_missing_category(self):
          # GH: 18185
          ser = Series([1, 2, 3, 1], dtype="category")
          msg = "'fill_value=-1' is not present in this Categorical's categories"
          with pytest.raises(TypeError, match=msg):
              ser.reindex([1, 2, 3, 4, 5], fill_value=-1)
  
      @pytest.mark.parametrize(
          "index_df,index_res,index_exp",
          [
              (
                  CategoricalIndex([], categories=["A"]),
                  Index(["A"]),
                  Index(["A"]),
              ),
              (
                  CategoricalIndex([], categories=["A"]),
                  Index(["B"]),
                  Index(["B"]),
              ),
              (
                  CategoricalIndex([], categories=["A"]),
                  CategoricalIndex(["A"]),
                  CategoricalIndex(["A"]),
              ),
              (
                  CategoricalIndex([], categories=["A"]),
                  CategoricalIndex(["B"]),
                  CategoricalIndex(["B"]),
              ),
          ],
      )
      def test_reindex_not_category(self, index_df, index_res, index_exp):
          # GH: 28690
          df = DataFrame(index=index_df)
          result = df.reindex(index=index_res)
          expected = DataFrame(index=index_exp)
          tm.assert_frame_equal(result, expected)
  