use new utilities, enable more markdown cells to be added easily

notebook/tests/selenium/test_markdown.py

@@ -24,11 +24,13 @@ def get_rendered_contents(nb):
 
 def test_markdown_cell(notebook):
     nb = notebook
-    nb[:] = ["# Foo"]
-    nb.convert_cell_type(0, cell_type="markdown")
-    for cell in nb:
-        nb.execute_cell(cell)
-    rendered_cells = nb.browser.find_elements_by_class_name('text_cell_render')
-    outputs = [x.get_attribute('innerHTML') for x in rendered_cells]
-    expected = '<h1 id="Foo">Foo<a class="anchor-link" href="#Foo">¶</a></h1>'
-    assert outputs[0].strip() == expected
+    cell_text = ["# Foo"]
+    expected_contents = ['<h1 id="Foo">Foo<a class="anchor-link" href="#Foo">¶</a></h1>']
+    for i, cell in enumerate(nb):
+        if i==0:
+            nb.convert_cell_type(0, cell_type="markdown")
+            nb[0] = cell_text[0]
+        nb.append(cell_text[1:], cell_type="markdown")
+    nb.run_all()
+    rendered_contents = get_rendered_contents(nb)
+    assert rendered_contents == expected_contents