seems that this runs deeper than I thought. Even in our code base, we tend to modify serverless and options after the fact.
We can refactor all test cases to move toward decoupling, however, I just want to make sure this is the path that we want to go.

On top of that, modifying this can possibly make other plugins break if they went for the 'hacky' way.

@sleepwithcoffee great thanks for giving that a spin!

seems that this runs deeper than I thought. Even in our code base, we tend to modify serverless and options after the fact.

When you spot such cases, do you think they intentionally update the global object, or it's more not envisioned side effect?

We can refactor all test cases to move toward decoupling, however, I just want to make sure this is the path that we want to go.

The ideal approach is to in first place, refactor all approached tests to rely on runServerless util (and ideally if each test file is covered with different PR). This can turn as bigger task, so maybe first let's list which of the failing tests happen in files that demand such refactoring. Some test files already have an existing guide on how to refactor them: https://github.com/serverless/serverless/issues?q=is%3Aopen+is%3Aissue+label%3Atests+label%3A%22good+first+issue%22)

I would say we have to refactor to decouple the test cases first. Right now, it is critical to run tests in order due to the way objects are initialized which is not good at all!

My take is every test should be dependent from each other. Tt makes our tests less error-prone and compatible with parallelization.

@sleepwithcoffee yes, that's a big problem with old tests, which focused to much on confirming implementation details which should not be the case. Refactoring test to rely on runServerless (so treating implementation as black box) fixes that. At the same time it's fine to remove completely test, that focus purely on internal implementation characteristics and not the outcome visible for user

Created PR #11812 to address the issue with tests, can merge that one first before moving on this one