Check _isMockFunction is true rather than truthy on global properties

[danrr]

Fixes #7009

Summary

resetModules checks if _isMockFunction is truthy on all properties of the global object, which can lead to TypeErrors when a global property is mocked using identity-obj-proxy. Changing the condition to check if _isMockFunction is true rather than truthy will fix the issue and keep the original intent of the code, so it shouldn't cause any breaking changes.

Test plan

Tests all ran OK.

[codecov-io]

Codecov Report

Merging #7017 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7017      +/-   ##
==========================================
+ Coverage   66.95%   66.95%   +<.01%     
==========================================
  Files         250      250              
  Lines       10430    10428       -2     
  Branches        4        4              
==========================================
- Hits         6983     6982       -1     
+ Misses       3446     3445       -1     
  Partials        1        1

Impacted Files	Coverage Δ
packages/jest-editor-support/src/Runner.js	74% <0%> (-0.26%)	⬇️
...est-cli/src/getNoTestFoundRelatedToChangedFiles.js	0% <0%> (ø)	⬆️

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[SimenB]

Mind fixing the ones in https://github.com/facebook/jest/blob/0418cab88c5e927c94a02ecb445fc694e6b2bbda/packages/jest-mock/src/index.js#L729-L731 as well?

Also, an integration test would be sweet 🙂

[danrr]

@SimenB thanks for having a look. I've updated the other instances of _isMockFunction being checked for truthiness but I'm not quite sure where best to have any new tests live.

[SimenB]

You can add an e2e test that uses identity-obj-proxy without blowing up 🙂

Look in https://github.com/facebook/jest/tree/master/e2e - all directories are "projects" which you can run with ../../../jest locally, and that we run - and assert on the output from, from __tests__ in https://github.com/facebook/jest/tree/master/e2e, where there usually is a test named similarly to a directory in the e2e directory.

[danrr]

@SimenB Thanks, I've added an e2e test and rebased

[SimenB]

Thanks!

[github-actions]

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