new_contents: from .. import api, spec, html
  
  
  def test_render():
      data = dict(x=[1, 2, 3],
                  y=[4, 5, 6])
      spec = api.Viz(data)
      s = spec.encode(x='x:Q', y='y:Q').mark_line()
      r = html.render(s)
      assert r is not None
subject: Add a simple test