PSXHAX Shoutbox MOTD and Twitter this weekend, and following Adrenaline with uma0 Support for USB mass storage by @BenMitnicK PlayStation Vita developer @voxel released a PS Vita TestKit Installer Deluxe VPK which allows installing full TestKit firmware on HENkaku Enso PS Vita consoles including Debug Settings and TestKit-specific utilities!
Download: Testkit_Installer_Deluxe.vpk / GIT
Below is a TestKit Installer Deluxe Installation video from Voxel9's YouTube Channel and some related tweets from his Twitter as well.
From the README.md, to quote: TestKit Installer Deluxe - Install TestKit firmware on HENkaku Enso PSVitas
This application can install (and uninstall) the TestKit firmware and TestKit spoofer plugin, which will completely enable Debug Settings from the settings apps, and everything else you can possibly do on an actual TestKit PS Vita. (such as Checker, Quick Sign Up, Installing debug packages in PKG installer, and even multiple PSN accounts.)
The installer makes modifications to vs0, and to the boot_config.txt, so don't power off your Vita or exit the app while installation is ongoing!
Finally, please be aware that this installer will not install on a PSTV, as there appears to be some compatibility issues with numerous things (TestKit FW was never designed for PSTV)
Q: Can I get an unrecoverable brick from this?
A: No. If your boot config corrupts (which it 99.9% should not do) then just reboot into safe mode, reinstall the 3.60 retail firmware, and reinstall HENkaku Enso. Moreover, it was proven that you could still access safe mode to reinstall firmware after deleting all of vs0.
Q: I get C2-12828-1 when trying to install/uninstall! Halp!
A: Make sure unsafe homebrew is on or try and untick/retick the box and it should work again.
TestKit Installer Deluxe Installation
Download: CexToRexPSTV.vpk / GIT