text: import unittest
  import pandas as pd 
  import numpy as np 
  from wrangle import Wrangle
  
  class WrangleMethodTester(unittest.TestCase):
  
      def test_null_checker(self):
  
          """
          Defines predetermined dataframe, runs it through the Wrangle 
          class and the null_checker function, then tests its output 
          against a predetermined result.
          """
  
          df = pd.DataFrame({'a': [5, 1, np.nan, 4], 'b': [2, np.nan, 12, np.nan]})
          df = Wrangle(df)
          self.assertEqual(df.null_checker(), print("There are 3 null values in this data frame."))
  
      def test_column_adder(self):
          
          """
          Defines two predetermined dataframes and a list, runs the first
          dataframe through the Wrangle class with predetermined parameters
          which is then run through the column_adder() function, and its 
          result is tested against the second dataframe using pd.shape and
          pd.columns.
          """
  
          df = pd.DataFrame({'a': [5, 1, np.nan, 4], 'b': [2, np.nan, 12, np.nan]})
          df2 = pd.DataFrame({'a': [5, 1, np.nan, 4], 'b': [2, np.nan, 12, np.nan], 'c': [15, 42, 6, np.nan]})
          my_list = [15, 42, 6]
          df = Wrangle(df, col_list=my_list, col_name='c')
          self.assertTrue(df.column_adder().shape == df2.shape)
          self.assertTrue(df.column_adder().columns.tolist(), df2.columns.tolist())
  
          
  
  if __name__ == "__main__":
      unittest.main()