text: import os
  
  import pandas as pd
  from pandas.testing import assert_frame_equal
  from powersimdata.network.usa_tamu.constants.zones import abv2state
  
  from prereise.gather.demanddata.nrel_efs.aggregate_demand import combine_efs_demand
  
  
  def test_combine_efs_demand():
      # Create a dummy data set
      cont_states = sorted(set(abv2state) - {"AK", "HI"})
      dummy_data = pd.DataFrame(
          1,
          index=pd.date_range("2016-01-01", "2017-01-01", freq="H", closed="left"),
          columns=cont_states,
      )
      dummy_data.index.name = "Local Time"
  
      # Create a dict containing four instances of dummy_data
      dummy_dict = {}
      for i in {"Transportation", "Residential", "Commercial", "Industrial"}:
          dummy_dict[i] = dummy_data
  
      # Generate the test result
      test_agg_dem = combine_efs_demand(efs_dem=dummy_dict)
  
      # Create the expected result
      exp_agg_dem = pd.DataFrame(
          4,
          index=pd.date_range("2016-01-01", "2017-01-01", freq="H", closed="left"),
          columns=cont_states,
      )
      exp_agg_dem.index.name = "Local Time"
  
      # Compare the two DataFrames
      assert_frame_equal(exp_agg_dem, test_agg_dem)
  