I have indeed done this before, but it was a long time ago against a code base far, far away, so the best I can do now is to give some things to try.
Your first ally in this battle is going to be
npm link. If you can get that to work correctly, it will be by far the simplest to deal with incrementally, as your changes in the fork will be reflected immediately.
However, sometimes projects just aren’t linkable. If you hit a dead end there, the next thing I would try is to put your fork on GitHub (where it probably is anyway) and refer to it in your test project
package.json using the syntax described here.
The last resort I’ve ever used is to follow the build instructions and take whereever that stuff is that gets published to npm (I forget which directory that is for Ionic, and it’s probably changed anyway since I did this) and literally dump a copy of it (I use
rsync, you can do it with
tar or probably even
cp) into the
node_modules of that test project. This method is far from optimal, as it requires manual intervention every time you change anything.
Let us know if any of this worked for you and good luck.