code: def test_read_evoked_besa_mul_incomplete(tmp_path):
      """Test reading incomplete BESA .mul files."""
      # Create BESA file with missing header fields and verify things don't break
      with open(f"{tmp_path}/missing.mul", "w") as f:
          f.write("SamplingInterval[ms]= 5\nCH1\n0\n")
      ev = read_evoked_besa(f"{tmp_path}/missing.mul")
      assert len(ev.ch_names) == len(ev.data) == 1
      assert ev.info["sfreq"] == 200
      assert ev.tmin == 0
      assert len(ev.times) == 1
      assert ev.ch_names == ["CH1"]
      assert ev.comment == ""
  
      # The SamplingInterval[ms] field (sample frequency) must exist
      with open(f"{tmp_path}/missing.mul", "w") as f:
          f.write("TimePoints= 1 Channels= 1\nCH1\n0\n")
      with pytest.raises(
          RuntimeError, match=r'No "SamplingInterval\[ms\]"'
      ):
          ev = read_evoked_besa(f"{tmp_path}/missing.mul")
  
imports: import inspect
  from pathlib import Path
  import pytest
  from mne.channels import read_custom_montage
  from mne.io import read_evoked_besa
label_desc: Use image node_id 3 for calling a global function with example usage: test_read_evoked_besa_mul_incomplete(tmp_path) without return types