code: def test_display_noconfig_nosystem_installed(monkeypatch):
      """
      Check that actually uses xvfbwrapper when installed (not mocked)
      and necessary (no config and $DISPLAY unset)
      """
      config._display = None
      if config.has_option("execution", "display_variable"):
          config._config.remove_option("execution", "display_variable")
      monkeypatch.delenv("DISPLAY", raising=False)
      newdisp = config.get_display()
      assert int(newdisp.split(":")[-1]) > 1000
      # Test that it was correctly cached
      assert config.get_display() == newdisp
  
file_path: nipype/nipype/utils/tests/test_config.py
imports: import os
  import sys
  import pytest
  from nipype import config
  from unittest.mock import MagicMock
label_desc: Use image node_id 11 for calling a global function with example usage: test_display_noconfig_nosystem_installed(monkeypatch) without return types