Using Jest's fakeTimers in modern mode breaks when also depending on @vue/cli-plugin-unit-jest

[Robin-Hoodie]

Version

4.5.11

Reproduction link

https://github.com/Robin-Hoodie/test-jest-modern-faketimers

Environment info

  System:
    OS: macOS 11.1
    CPU: (12) x64 Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
  Binaries:
    Node: 15.0.1 - ~/.nvm/versions/node/v15.0.1/bin/node
    Yarn: 1.22.5 - ~/.yarn/bin/yarn
    npm: 7.0.3 - ~/.nvm/versions/node/v15.0.1/bin/npm
  Browsers:
    Chrome: 88.0.4324.96
    Edge: 88.0.705.53
    Firefox: 84.0.2
    Safari: 14.0.2
  npmPackages:
    @vue/cli-plugin-unit-jest: ^4.5.11 => 4.5.11 
    @vue/cli-shared-utils:  4.5.11 
    jest-serializer-vue:  2.0.2 
    vue-jest:  3.0.7 
    vue-template-es2015-compiler:  1.9.1 
  npmGlobalPackages:
    @vue/cli: Not Found

Steps to reproduce

• Clone repo
• Run command "yarn jest"

What is expected?

Using Jest's fakeTimers in modern mode should work (https://jestjs.io/blog/2020/05/05/jest-26#new-fake-timers)

What is actually happening?

An error is thrown: "TypeError: setSystemTime is not available when not using modern timers"

---

I'm honestly not sure whether this is a Jest issue, a Vue CLI issue or a Yarn issue.

This can be fixed by removing the dependency on @vue/cli-plugin-unit-jest entirely, though that's obviously not ideal.

It seems that somehow, running jest while having a dependency on @vue/cli-plugin-unit-jest will still use jest@24
Even overwriting the jest@24 dependency to jest@26 using Yarn resolutions does not fix the issue.

I bumped into this while working on a monorepo where I have have 2 sub packages in my workspace:

• A server package in which tests are run with jest
• A client (Vue) package in which tests are run with vue-cli-service test:unit

(The error message is slightly different there, logging "TypeError: Cannot read property 'useFakeTimers' of undefined", though the root cause is likely the same)

EDIT: Just found out that installing dependencies with npm i (first removing yarn.lock and node_modules) will actually also fix this (though that doesn't convince me yet that this is a yarn issue)

EDIT#2: Using yarn 2 to install dependencies also removes this problem

[willianrod]

I had the same error but when testing Strapi. Maybe something with Jest

[dave0688]

Any help would be appreciated here. I just ran into the same issue, no solution found yet.

[FrozenKiwi]

EDIT: original comment was wrong:

Posting solution here (as this was the first issue in my google):

jestjs/jest#11662

In my case it jest-environment-uint8array introducing a version conflict.

[MaxWeisen]

I am receiving this error when calling jest.useFakeTimers('modern') in my test spec

typeerror: cannot read property 'usefaketimers' of undefined

When I run yarn why @jest/fake-timers I see that vue-cli depends on @jest/fake-timers @24.9.0 while the rest of my packages depend on @jest/fake-timers @26.6.2

Seems like a version mismatch.

I am using Yarn v1.22.15