old_contents: from carculator.background_systems import BackgroundSystemModel
  import pytest
  
  
  def test_size_dictionary():
      bs = BackgroundSystemModel()
      assert len(bs.electricity_mix) == 89
      assert int(bs.electricity_mix.sel(country="FR").values.sum()) == 10
      assert int(bs.electricity_mix.sel(country="FR", year=2015).values.sum()) == 1
  
  
  def test_cumulative_losses():
      bs = BackgroundSystemModel()
      assert len(bs.losses) == 147
      assert float(bs.losses["AL"]["LV"]) > 1.1
  
new_contents: from carculator.background_systems import BackgroundSystemModel
  import pytest
  
  
  def test_size_dictionary():
      bs = BackgroundSystemModel()
      assert len(bs.electricity_mix) == 90
      assert int(bs.electricity_mix.sel(country="FR").values.sum()) == 10
      assert int(bs.electricity_mix.sel(country="FR", year=2015).values.sum()) == 1
  
  
  def test_cumulative_losses():
      bs = BackgroundSystemModel()
      assert len(bs.losses) == 147
      assert float(bs.losses["AL"]["LV"]) > 1.1
  
subject: Update test_background_systems.py