class_docstr: Test the ProjectionVisualizer base class
class_docstr_tok: ["Test","the","ProjectionVisualizer","base","class"]
docstr: Assert single color plot when y is not specified
docstr_tok: ["Assert","single","color","plot","when","y","is","not","specified"]
code: def test_single_plot(self):
      """
      Assert single color plot when y is not specified
      """
      X, y = self.discrete
      visualizer = MockVisualizer(projection=2, colormap="plasma")
      visualizer.fit_transform(X)
      visualizer.finalize()
      self.assert_images_similar(visualizer)
  
imports: import pytest
  import numpy.testing
  import matplotlib.pyplot
  from yellowbrick.features.projection import *
  from yellowbrick.exceptions import YellowbrickValueError
  from tests.base import VisualTestCase
  from unittest import mock
  from sklearn.decomposition import PCA
  from sklearn.pipeline import Pipeline
  from sklearn.preprocessing import StandardScaler
label_desc: Use image node_id 4 for calling the TestProjectionVisualizer obj's underlying member method code with example usage: obj.test_single_plot() without return types