new_contents: #!/usr/bin/env python
  from six import StringIO
  
  from cliff.formatters import shell
  
  import mock
  
  
  def test_shell_formatter():
      sf = shell.ShellFormatter()
      c = ('a', 'b', 'c')
      d = ('A', 'B', 'C')
      expected = 'a="A"\nb="B"\n'
      output = StringIO()
      args = mock.Mock()
      args.variables = ['a', 'b']
      args.prefix = ''
      sf.emit_one(c, d, output, args)
      actual = output.getvalue()
      assert expected == actual
  
subject: Add unit test for shell formatter