'``ProcessNode.get_output()`` runs a command that is the combination of
the initial arguments and the ones given to ``get_output()``.'

def test_get_output_runs_command(self):

    node = ProcessNode(initial_command_arguments=['sh'])
    temp_file = self.mktemp()
    node.get_output(['-c', ('echo    hello    >    ' + temp_file)])
    self.assertEqual(FilePath(temp_file).getContent(), 'hello\n')
