code: def test_default_plot_generates_expected_html(self):
      layout_json = pio.json.to_json_plotly(fig["layout"])
  
      html = self._read_html(
          plotly.offline.plot(
              fig, auto_open=False, filename=html_filename
          )
      )
  
      # I don't really want to test the entire script output, so
      # instead just make sure a few of the parts are in here?
      self.assertIn("Plotly.newPlot", html)  # plot command is in there
  
      x_data = '"x":[1,2,3]'
      y_data = '"y":[10,20,30]'
  
      self.assertTrue(
          x_data in html and y_data in html
      )  # data in there
      self.assertIn(layout_json, html)  # so is layout
      self.assertIn(plotly_config_script, html)  # so is config
      self.assertIn(PLOTLYJS, html)  # and the source code
      # and it's an <html> doc
      self.assertTrue(
          html.startswith("<html>") and html.endswith("</html>")
      )
  
imports: import json
  import os
  from unittest import TestCase
  import pytest
  import plotly
  import plotly.io
  from plotly.io._utils import plotly_cdn_url
label_desc: Use image node_id 4 for calling the PlotlyOfflineTestCase obj's underlying member method code with example usage: obj.test_default_plot_generates_expected_html() without return types