if(NOT APPLE)
  # GLUT tests don't work on Apple.
  # see discussion on vtk/vtk!5169

  find_package(GLUT REQUIRED)

  vtk_add_test_cxx(vtkRenderingExternalCxxTests tests
    TestGLUTRenderWindow.cxx
    )

  vtk_test_cxx_executable(vtkRenderingExternalCxxTests tests)
  target_link_libraries(vtkRenderingExternalCxxTests PRIVATE
    GLUT::GLUT)
endif()