old_contents: from cno.datasets import ToyMMB
  
  
  
  def test_datasets_toymmb():
  
      ToyMMB.data.df
      ToyMMB.model
      ToyMMB.description
  
new_contents: import os
  from cno.datasets import ToyMMB
  from cno.datasets import cnodata, registers
  
  
  def test_registered_cnodata():
      for filename in registers:
          fullpath = cnodata(filename)
          assert os.path.exists(fullpath)
  
      try:
          cnodata('dummy')
          assert False
      except:
          assert True
  
  def test_datasets_toymmb():
  
      ToyMMB.model_filename
      ToyMMB.data_filename
      ToyMMB.description
      ToyMMB.plot()
  
subject: update tests