Properly wait for LTI stub's buttons to render

common/djangoapps/terrain/stubs/lti.py

@@ -191,13 +191,13 @@ class StubLtiHandler(StubHttpRequestHandler):
         if submit_url:
             submit_form = textwrap.dedent("""
                 <form action="{submit_url}/grade" method="post">
-                    <input type="submit" name="submit-button" value="Submit">
+                    <input type="submit" name="submit-button" value="Submit" id="submit-button">
                 </form>
                 <form action="{submit_url}/lti2_outcome" method="post">
-                    <input type="submit" name="submit-lti2-button" value="Submit">
+                    <input type="submit" name="submit-lti2-button" value="Submit" id="submit-lti-button">
                 </form>
                 <form action="{submit_url}/lti2_delete" method="post">
-                    <input type="submit" name="submit-lti2-delete-button" value="Submit">
+                    <input type="submit" name="submit-lti2-delete-button" value="Submit" id="submit-lti-delete-button">
                 </form>
             """).format(submit_url=submit_url)
         else:

lms/djangoapps/courseware/features/lti.py

@@ -359,6 +359,7 @@ def click_grade(_step, version):
     location = world.scenario_dict['LTI'].location.html_id()
     iframe_name = 'ltiFrame-' + location
     with world.browser.get_iframe(iframe_name) as iframe:
+        world.wait_for_visible('#' + version_map[version]['selector'])
         iframe.find_by_name(version_map[version]['selector']).first.click()
         assert iframe.is_text_present(version_map[version]['expected_text'])