How do you test file uploads without keeping a folder of random fixtures?

Every file-upload bug seems to start with the same request:

“Can you find me a 10 KB PNG?”

“Do we have a video with a predictable size?”

“What happens if the extension and file signature disagree?”

I used to keep a messy folder of test files for this. Half the files had unclear origins, the names were unreliable, and reproducing an exact boundary case took longer than testing the actual feature.

So I built TestFiles.

It generates test files locally in the browser, including exact-size images, audio, text, and other common fixtures. It also lets you inspect magic bytes, MIME information, and file signatures without uploading the file to a server.

For media and document workflows, there are stable sample files that can be used in automated tests. The goal is simple: make upload limits, MIME validation, Range requests, and malformed-file handling easier to reproduce.

I’m curious how other developers and QA engineers manage fixtures today. Do you keep them in the repository, generate them during tests, or download them from a shared location?

You can try it here: https://testfiles.dev