new_contents: from main.tests.helper_methods import get_command_with_parsed_options
  
  
  def test_prepare_package_filters_returns_none_when_no_package_filters():
      merge_coverage_files_command = get_command_with_parsed_options({
          'packagefilters': [],
      })
  
      assert merge_coverage_files_command.prepare_packagefilters() is None
  
  
  def test_prepare_package_filters_converts_filters_to_regex():
      merge_coverage_files_command = get_command_with_parsed_options({
          'packagefilters': ['missingletters', 'test1.class', 'test2.*'],
      })
  
      assert ['^missingletters$', '^test1\.class$', '^test2\..*$'] == merge_coverage_files_command.prepare_packagefilters()
subject: Add tests for preparing filters