Download a really big file in your device (I tested this with 500MB files, but you should check the max file upload in your server). You can download one from here . In Android or desktop, just download the file. In iOS, store the file in iCloud. Login in a Moodle site as admin and go to Site administration > Security > Site security settings. Set a big userquota (enough to upload the file from the previous step). Please notice that the server also defines a maximum upload size. In the app, login as a student and go to your private files. Click to upload a new file.  In Android or desktop, select the "File" option and select the file you downloaded in step 1. In iOS, select "More..." and select the file you downloaded in step 1 (it should be in "Recent" or in iCloud, depending on the iOS version). Check that the file is successfully uploaded. Please notice it can take a while (a 500MB file took around 4 minutes to read the file in an Android 7 phone).