Issues when running jest with coverage for all packages within a lerna monorepo

首先比较从 package 目录运行的 Jest coverage 与从 Lerna repository 根目录运行的 coverage，重点关注 node_modules/jsdom-worker/src/index.js:89 以及从另一个 monorepo package 导入的函数。重现 ReferenceError，并确定为什么 cov_* instrumentation 会到达 worker；当 root 级别的 coverage 运行不再出现此故障时即表示完成。

I am not 100% sure if my problem really is jsdom-worker related but I guess here is my best starting point:

I am currently working on a lerna monorepo where one of the packages executes a function in a worker. I therefore included jsdom-worker in the corresponding test for this package. The function is an export from a different file of this package. I had to add /* istanbul ignore file */ to it because otherwise the coverage would fail due to cov_* variables added during testing not being reachable for the worker. Jest is used for testing and coverage.

So far this would be OK - and tests as well as coverage run just fine when run localy from within the package.

But if I do run the coverage from the root directory it always fails with ReferenceError: cov_2j8vgqrgle is not defined in node_modules/jsdom-worker/src/index.js:89:18.

The function that is run in the worker has a function imported from another package of the monorepo and if I do run global coverage (remember: running coverage from within the package is 100% fine) this one seems to be interpreted and cov_* gets added to it which is guaranteed to fail.

Any idea what goes wrong and if there is anything I can do about it?