Fix TypeError with babel-register's cache

[xtuc]

Q	A
Patch: Bug Fix?	yes
Major: Breaking Change?
Minor: New Feature?
Deprecations?
Spec Compliancy?
Tests Added/Pass?
Fixed Tickets	#5259
License	MIT
Doc PR
Dependency Changes

Follow up from #5259.

[mention-bot]

@xtuc, thanks for your PR! By analyzing the history of the files in this pull request, we identified @sindresorhus, @jonathanong and @SimenB to be potential reviewers.

[xtuc]

I took this opportunity to add some tests to babel-register's cache. It is quite difficult to do.

Could you tell me what do you think about this test suite. Should we modify the code to make it more testable? Because we can't cover all the cases right now.

[babel-bot]

Hey @xtuc! It looks like one or more of your builds have failed. I've copied the relevant info below to save you some time.

• Node v7 - linux

[existentialism]

Funny enough, the reason the tests fail during the coverage run is because nyc sets BABEL_DISABLE_CACHE=1 😆

[xtuc]

Oh, you're right 👍 Thanks for pointing out this to me.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@283d9cb). Click here to learn what that means.

@@            Coverage Diff            @@
##             master    #5260   +/-   ##
=========================================
  Coverage          ?   89.34%           
=========================================
  Files             ?      204           
  Lines             ?     9912           
  Branches          ?     2666           
=========================================
  Hits              ?     8856           
  Misses            ?     1056           
  Partials          ?        0

Impacted Files	Coverage Δ
packages/babel-register/src/cache.js	81.81% <100%> (ø)

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[hzoo]

Nice work both of you!