code: def test_check_univariate(self):
      with assert_raises(ValueError):
          MAD().fit(X=[[0.0, 0.0], [0.0, 0.0]])
      with assert_raises(ValueError):
          MAD().decision_function(X=[[0.0, 0.0], [0.0, 0.0]])
  
imports: from __future__ import division
  from __future__ import print_function
  import os
  import sys
  import unittest
  from numpy.testing import assert_allclose
  from numpy.testing import assert_array_less
  from numpy.testing import assert_equal
  from numpy.testing import assert_raises
  from scipy.stats import rankdata
  from sklearn.base import clone
  from sklearn.metrics import roc_auc_score
  from pyod.models.mad import MAD
  from pyod.utils.data import generate_data
label_desc: Use image node_id 22 for calling the TestMAD obj's underlying member method code with example usage: obj.test_check_univariate() without return types