class_docstr: Test the RFECV visualizer
class_docstr_tok: ["Test","the","RFECV","visualizer"]
docstr: Test step hyperparam validation
docstr_tok: ["Test","step","hyperparam","validation"]
code: def test_invalid_step(self, step):
      """
      Test step hyperparam validation
      """
      with pytest.raises(
          YellowbrickValueError, match="step must be >0"
      ):
          oz = RFECV(SVC(kernel="linear"), step=step)
          oz.fit(self.dataset.X, self.dataset.y)
  
imports: import sys
  import pytest
  import numpy
  import numpy.testing
  from unittest.mock import patch
  from tests.fixtures import Dataset
  from tests.base import VisualTestCase
  from yellowbrick.model_selection.rfecv import *
  from yellowbrick.datasets import load_occupancy
  from yellowbrick.exceptions import YellowbrickValueError
  from sklearn.svm import SVC
  from sklearn.datasets import make_classification
  from sklearn.model_selection import ShuffleSplit
  from sklearn.model_selection import StratifiedKFold
  from sklearn.linear_model import LogisticRegression
  from sklearn.ensemble import RandomForestClassifier
label_desc: Use image node_id 6 for calling the TestRFECV obj's underlying member method code with example usage: obj.test_invalid_step(step) without return types