'There are multiple mobx instances active' error caused by jest mocks

[vonovak]

I think more people will run into this or already did, perhaps we can discuss the solution. This is a question / issue that I have met while upgrading mobx 3.3 to 4.3. It's of course possible this is more a Jest problem rather than MobX, but I'm posting here for better visibility.

I'm using Jest 23 for tests and after the upgrade, when I run the tests, I get:

Error: [mobx] There are multiple mobx instances active. This might lead to unexpected results. See https://github.com/mobxjs/mobx/issues/1082 for details.

I only encounter the problem when running tests. The problem stems from jest.genMockFromModule (and possibly Jest's other mocking mechanisms). It is reproducible by creating a mock of a module that imports from mobx. A minimal repro is here - just clone it, install and run npm t.

Solution

I'm still looking for a proper one. I have tried using

import { configure } from 'mobx';
configure({ isolateGlobalState: true });

in the setup file but it seems like there is some sort of asynchronous behavior involved - it does improve things, but fails with the same error at some point.

Any pointers appreciated. Thanks!

[mweststrate]

This seems to be caused by jestjs/jest#4940, if I you add a console.trace() to node_modules/mobx/mobx.js you will indeed see that Jest does not cache the module, but includes it twice:

  console.error console.js:188
    [object Object]
        at Object.<anonymous> (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/mobx/lib/mobx.js:2873:13)
        at Runtime._execModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:694:13)
        at Runtime.requireModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:376:14)
        at Runtime.requireModuleOrMock (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:463:19)
        at Object.<anonymous> (/home/michel/Desktop/tmp/mobxMultipleInstances/src/User.js:1:1)
        at Runtime._execModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:694:13)
        at Runtime.requireModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:376:14)
        at Runtime.requireModuleOrMock (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:463:19)
        at Object.<anonymous> (/home/michel/Desktop/tmp/mobxMultipleInstances/src/__tests__/User.unit.test.js:1:1)
        at Runtime._execModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:694:13)

  console.error console.js:188
    [object Object]
        at Object.<anonymous> (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/mobx/lib/mobx.js:2873:13)
        at Runtime._execModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:694:13)
        at Runtime.requireModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:376:14)
        at Runtime.requireModuleOrMock (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:463:19)
        at Object.<anonymous> (/home/michel/Desktop/tmp/mobxMultipleInstances/src/MyClass.js:1:1)
        at Runtime._execModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:694:13)
        at Runtime.requireModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:376:14)
        at Runtime._generateMock (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:739:34)
        at Object.genMockFromModule (/home/michel/Desktop/tmp/mobxMultipleInstances/node_modules/jest-runtime/build/index.js:957:45)
        at Object.genMockFromModule (/home/michel/Desktop/tmp/mobxMultipleInstances/src/__mocks__/MyClass.js:3:26)

[mweststrate]

You can now upgrade to MobX 4.4 / 5.1, which can work around this error

[EQuimper]

@mweststrate still get this error even after upgrading to version 5.1 I want to unit test a model build with mobx-state-tree and have the same error.

[mweststrate]

Please open a new issue with small reproduction. Similar symptoms are not necessarily the same cause. Op ma 27 aug. 2018 22:51 schreef Emanuel Quimper <[email protected]>:

…

@mweststrate <https://github.com/mweststrate> still get this error even after upgrading to version 5.1 I want to unit test a model build with mobx-state-tree and have the same error. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1672 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABvGhNdEPRjcIfGbjiYMeWXYChCNEpstks5uVFvUgaJpZM4V1WXW> .

[EQuimper]

@mweststrate I just make it work, in react-native I put globals window: true when it should be an empty object. Sorry for this

[jayshah123]

This used to be a warning in previous mobx versions, on the latest mobx versions it straight out crashes. I will raise the issue with an example test/demo.