Tests unexpectedly fail in Node 6

[m-allanson]

Do you want to request a feature or report a bug?
This might be a bug.

What is the current behavior?
I have a small set of tests that pass on Node 8, but fail on Node 6.

The tests have a beforeEach() that resets the state of two global properties. Each test then sets the properties to different values before making assertions. in Node 6 it seems that the beforeEach reset isn't being applied.

There's a basic demo repo here: https://github.com/m-allanson/jest-global-test

Which is based on the behaviour found here: gatsbyjs/gatsby#3233

What is the expected behavior?
The tests should pass in both Node 8 and Node 6.

Jest version: 22.0.3
Yarn version: 1.3.2
Node 6 version: 6.12.2
Node 8 version: 8.9.3
OS: MacOS Sierra 10.12.6 (also observed in Travis CI's Trusty environment https://travis-ci.org/gatsbyjs/gatsby/builds/319991766)

[thymikee]

IIRC this was a bug in Node 6 fixed in Node 8 while rewriting some VM specific logic. I can’t search for it currently because I’m on a shitty mobile connection. You can usually bypass it by setting these values to undefined

[m-allanson]

That's great 👍, thanks for the swift reply.

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