Create an assignment requiring file upload but without requiring students to click the Submit button.

Log in as a test student, go to the upload assignment, click on Add submission. On the File submission page, DO NOT submit a file, just click on Save changes. You will be right back on the File submissions page with a message saying Nothing was submitted.

Now as admin go look at the logs. Even though nothing was uploaded the logs will say there was was. If you go click Save changes again, the logs will show, Submission updated, while the File submissions page is still saying Nothing was submitted. In fact, if the student just refreshes the page, the logs will show another, Submission updated.