docstr: Tests if the data module functions properly when no normal_test_dir is provided.
code: def test_normal_test_dir_omitted(
      self, make_data_module, test_split_mode
  ):
      """Tests if the data module functions properly when no normal_test_dir is provided."""
      data_module = make_data_module(
          dataset="folder",
          test_split_mode=test_split_mode,
          normal_test_dir=None,
      )
      # check if we can retrieve a sample from every subset
      next(iter(data_module.train_dataloader()))
      next(iter(data_module.test_dataloader()))
      next(iter(data_module.val_dataloader()))
      # the test set should contain normal samples which are sampled from the train set
      assert data_module.test_data.has_normal
  
imports: import os
  import numpy
  import pytest
  from anomalib.config import update_input_size_config
  from anomalib.data import Avenue, BTech, Folder, MVTec, ShanghaiTech, UCSDped, Visa, get_datamodule
  from anomalib.data.utils import DirType
  from anomalib.pre_processing.transforms import Denormalize, ToNumpy
  from tests.helpers.config import get_test_configurable_parameters
  from tests.helpers.dataset import TestDataset, get_dataset_path
label_desc: Use image node_id 3 for calling the TestSubsetSplitting obj's underlying member method code with example usage: obj.test_normal_test_dir_omitted(make_data_module, test_split_mode) without return types