text: """Test layer extracting functionality."""
  import numpy as np
  import pymatgen as mg
  import pytest
  from megnet.data.crystal import CrystalGraph
  
  from unlockgnn.datalib import preprocessing as preproc
  
  test_index = 1
  cg = CrystalGraph()
  
  cubic_lattice = mg.Lattice.cubic(4.2)
  cscl = mg.Structure(cubic_lattice, ["Cs", "Cl"], [[0, 0, 0], [0.5, 0.5, 0.5]])
  
  
  @pytest.fixture
  def layer_extractor(mocker):
      """Create a layer_extractor instance with a mock model."""
      mock_model = mocker.MagicMock()
      mock_model.graph_converter = cg
      mocker.patch("tensorflow.keras.backend.function")
      return preproc.LayerExtractor(mock_model, test_index)
  
  
  def test_extractor_init(layer_extractor):
      """Test the initialization procedure for the `LayerExtractor`."""
      layer_extractor.model.layers.__getitem__.assert_called_with(test_index)
      assert callable(layer_extractor.layer_eval)
  
  
  def test_struct_conversion(layer_extractor):
      """Test converting a structure to an input."""
      converted = layer_extractor._convert_struct_to_inp(cscl)
      assert isinstance(converted, list)
      assert all(isinstance(x, np.ndarray) for x in converted)
  
  
  # TODO: Lightweight solution to check shape outputs
  
  
  def test_get_layer_out(layer_extractor):
      """Test getting layer outputs."""
      layer_extractor.get_layer_output(cscl)
      layer_extractor.layer_eval.assert_called_once()
  
  
  def test_get_layer_out_graph(layer_extractor):
      """Test getting layer outputs for a graph."""
      cscl_graph = cg.convert(cscl)
      layer_extractor.get_layer_output_graph(cscl_graph)
      layer_extractor.layer_eval.assert_called_once()
  