Tests isolation

[piranna]

Instead of using Workers, use cluster module ir child_process. This way, they would be full y independent processes so they would not share global atte, the same way Jest default environment does, and Aldo native chdir can be used.

[nicolo-ribaudo]

Workers don't share global state between each other.

Jest gets test isolation by running every test in a new "vm context", using the vm Node.js module. The purpose of this runner is to avoid dong that, which means that we cannot have tests isolation.

(technically, we could spawn a new worker/process for every test: however, that would make the runner painfully slower, probably orders of magnitude slower than the default Jest runner).

[bajtos]

(technically, we could spawn a new worker/process for every test: however, that would make the runner painfully slower, probably orders of magnitude slower than the default Jest runner).

How about spawning a new worker process per test file? It would give us partial isolation - the global state is shared by all tests in a single file but not between different test files. The downside is the slightly more complex mental model - a change in the global state affects some tests but not all.