There are definitely homebrew for testing peripherals in addition to official test media.
I've actually used them regularly in emulators to verify my DualShock3 pad is working appropriately in Playstation and Dreamcast emulators as I mapped the L2/R2 analog buttons each to a half-axis and that type of configuration doesn't always play nice with all software.
For example, there is the Dreamcast DJ Controller Test:
If you're interested in anything specific, I can check what I have and see what I can link you if you there is a specific system you're interested in.