In an assignment, students can add and edit text online

This test requires an assignment with online text set to yes and file submissions set to no.

1. Log in as a student, go to the assignment and click the 'Add submission' button.
2. Check that you are not allowed to save changes if you have not entered any text.
3. Add some text, then click the 'Save changes' button.
4. Check that the text has been saved and that the submission status is shown as 'Submitted for grading'.
5. Click the 'Edit my submission' button, edit the text, then click the 'Save changes' button.
6. Check that the changes have been saved and that the last modified date and time are correctly displayed.