Recent enhancements to the Frida open-source dynamic instrumentation toolkit greatly ease the process of conducting jailed testing. You no longer have to manually package the Frida Gadget in your target app. As long as the app is debuggable, Frida does that for you. This post will walk you through the process of using Frida on a jailed device.
Frida version 12.7.12 and above include this improvement. Frida 12.8 is the most current version as of late December 2019.
These instructions were written using macOS and assume access to Xcode for re-signing applications. You will need to install Frida 12.7.12 or above and target a device running iOS 13.
To continue with full technical overview, go here: https://www.nowsecure.com/blog/2020/01/02/how-to-conduct-jailed-testing-with-frida/