old_contents: """ module for the class for core of the application """
  
  import pytest
  from click.testing import CliRunner
  from exch.core import cli
  from exch.helpers import fixer, google_finance_converter
  
  @pytest.fixture
  def runner():
      return CliRunner()
  
  def test_same_currency_code():
      """ when the same currency is base as well as target """
      result_usd = runner().invoke(cli, ['-f', 'USD', '-t', 'USD'])
      assert result_usd.exit_code == 0
      assert result_usd.output == "1.00\n"
  
      result_inr = runner().invoke(cli, ['-f', 'INR', '-t', 'INR'])
      assert result_inr.exit_code == 0
      assert result_inr.output == "1.00\n"
  
  def test_fixer_usd_to_inr_():
      """ base: USD, target: INR, on the date of 2017-05-12 """
      assert fixer('USD', 'INR', date='2017-05-12') == round(64.307, 2)
  
  def test_fixer_usd_to_jpy_():
      """ base: USD, target: JPY, on the date of 2017-05-12 """
      assert fixer('USD', 'JPY', date='2017-05-12') == round(113.85, 2)
  
  
  #def test_fixer_inavlid_currency():
  #    """ when invalid currency is passed to fixer.io """
  #    pass
  
  #def test_fixer_invalid_value_type():
  #    """ when invalid value type is passed to fixer """
  #    pass
  
new_contents: """ unit testing the helper functions """
  
  from exch.helpers import fixer
  
  def test_fixer_same_currency_code():
      """ when the same currency is base as well as target """
      assert fixer('USD', 'USD', 1) == 1.00
      assert fixer('INR', 'INR', 1) == 1.00
  
  def test_fixer_usd_to_inr():
      """ fixer_io base: USD, target: INR, on date 2017-05-12 """
      assert fixer('USD', 'INR', 1, date='2017-05-12') == round(64.307, 2)
  
  def test_fixer_usd_to_jpy():
      """ fixer_io base: USD, target: JPY, on date 2017-05-12 """
      assert fixer('USD', 'JPY', 1, date='2017-05-12') == round(113.85, 2)
  
  def test_fixer_gbp_to_php_value_99():
      """ fixer_io base: GBP, target: PHP, on date 2017-05-12, value: 99 """
      assert fixer('GBP', 'PHP', 99, date='2017-05-12') == round(63.942 * 99, 2)
  
  def test_fixer_inavlid_currency():
      """ when invalid currency is passed to fixer.io """
      assert fixer('USD', 'TTT', 1) == "Invalid currency"
      assert fixer('HHRR', 'TTT', 1) == "Invalid currency"
  
  # TODO: test for connection error
  
subject: refactor fixer_io unit tests