I ran the software through the certification and caught a few nits:
The error return is 'failure' not 'error'
The spec says that it needs to return 'failure' for out of range or non-numeric grades
The result score needs a language tag, hard-coded as 'en'
Setting a grade multiplied by 100 but reading the grade did not divide by 100
All those are now fixed with this patch as well as this bit of cruft:
I removed the "extension service url" as it is not implemented in service.php
Feel free to review and adjust - probably the one place you might want to refactor
is that I put code to catch out-of-range-and non-numeric in
lti_parse_grade_replace_message and threw an exception on error and then caught
it in service.php and sent back the 'failure' message. Feel free to refactor a
bit if you see this done in a cleaner manner.
