code: def test_reg_tools_mul():
      """tests for reg_tools interface"""
      # Create a reg_tools object
      nr_tools = RegTools()
  
      # Check if the command is properly defined
      assert nr_tools.cmd == get_custom_path("reg_tools")
  
      # test raising error with mandatory args absent
      with pytest.raises(ValueError):
          nr_tools.run()
  
      # Test reg_tools: mul
      in_file = example_data("im1.nii")
      nr_tools.inputs.in_file = in_file
      nr_tools.inputs.mul_val = 4
      nr_tools.inputs.omp_core_val = 4
  
      cmd_tmp = "{cmd} -in {in_file} -mul 4.0 -omp 4 -out {out_file}"
      expected_cmd = cmd_tmp.format(
          cmd=get_custom_path("reg_tools"),
          in_file=in_file,
          out_file="im1_tools.nii.gz",
      )
  
      assert nr_tools.cmdline == expected_cmd
  
      # Test reg_tools: iso
      nr_tools_2 = RegTools(iso_flag=True, omp_core_val=4)
      in_file = example_data("im1.nii")
      nr_tools_2.inputs.in_file = in_file
  
      cmd_tmp = "{cmd} -in {in_file} -iso -omp 4 -out {out_file}"
      expected_cmd = cmd_tmp.format(
          cmd=get_custom_path("reg_tools"),
          in_file=in_file,
          out_file="im1_tools.nii.gz",
      )
  
      assert nr_tools_2.cmdline == expected_cmd
  
file_path: nipype/nipype/interfaces/niftyreg/tests/test_regutils.py
imports: import os
  import pytest
  from ....utils.filemanip import which
  from ....testing import example_data
  from ..None import get_custom_path, RegAverage, RegResample, RegJacobian, RegTools, RegMeasure, RegTransform
label_desc: Use image node_id 4 for calling a global function with example usage: test_reg_tools_mul() without return types