As admin, make sure unoconv is the only document converter enabled. [Site admin > Plugins > Document converters > Manage document converters] . Verify unoconv is working by checking the test page on it's settings page (click 'settings' from the manage converters page). Create a course, enrol a student and a teacher. Create an assignment allowing file submissions and don't restrict the file types allowed. As the student submit a jpg file to the assignment with the '.jpg' file extension (not jpe, not jpeg). So that this submission doesn't collide with prior conversion attempts, please make sure to rename any existing jpeg file before uploading it, eg. testfile.jpg to testfile-1.jpg. This will ensure reconversion for this file type. Now, as the teacher, login and grade the assignment. Verify you see the converted JPEG and not just an empty page. Repeat the test for files with extensions .jpeg and .jpe (also under the image/jpeg mimetype) and confirm these fail to convert. The unoconv converter doesn't support these extensions. Repeat the test using the original, working jpg file, but this time remove the extension before uploading the file. Confirm this fails to convert.