code: def test_lut():
      for op in (
          "corner",
          "dilation4",
          "dilation8",
          "erosion4",
          "erosion8",
          "edge",
      ):
          lb = ImageMorph.LutBuilder(op_name=op)
          assert lb.get_lut() is None
  
          lut = lb.build_lut()
          with open(f"Tests/images/{op}.lut", "rb") as f:
              assert lut == bytearray(f.read())
  
imports: import pytest
  from PIL import Image, ImageMorph, _imagingmorph
  from .helper import assert_image_equal_tofile, hopper
label_desc: Use image node_id 8 for calling a global function with example usage: test_lut() without return types