Can't be tested with Jest

[nirsky]

Seems like Jest magic on the require function is clashing with require-in-the-middle.
Not sure if there's a way to overcome this.
Decided to open this issue to discuss this, maybe someone can share a solution.

Related:

• https://overengineered.thoughts.lt/testing-imports/
• Jest Overwriting Require? jestjs/jest#7722

[astorm]

Hello @nirsky, thanks for bringing this up. To start the conversation, two questions

1. Do you have an example of some jest code where require-in-the-middle doesn't work like you expect?
2. Do you happen to know what, specifically, "jest magic on the require function" is and/or where in jest they're applying this magic?

[nirsky]

Hey, sorry for the late reply.
I encountered this issue while writing tests for plugins I wrote for opentelemetry.
opentelemetry uses require-in-the-middle to know when a library was required, and patch it upon requiring it.

Jest is overriding the require to create an isolated environment for each test suite, mocking and JIT (jestjs/jest#7722).
I suspect those 2 collide.
In my case I had to migrate all the tests to use mocha.

[watson]

You're correct regarding jest vs require-in-the-middle. Jest uses the vm core module to run tests. I've spent a lot of time to see if we could somehow be notified of calls to require from within those vm's, but so far no luck. It should be technically possible, but jest is very complicated, so I've not been able to figure out what change I need to make to jest in order for it to work. So for now I've tabled the efforts as it was taking too much time.