code: def test_select_diff(competences, expected):
      rng = np.random.RandomState(123456)
      dcs_test = BaseDCS(
          selection_method="diff", diff_thresh=0.15, random_state=rng
      )
  
      selected_clf = dcs_test.select(np.array(competences))
      assert np.allclose(selected_clf, expected)
  
imports: from unittest.mock import MagicMock
  import numpy
  import pytest
  from deslib.dcs.base import BaseDCS
label_desc: Use image node_id 7 for calling a global function with example usage: test_select_diff(competences, expected) without return types