Error during jest test execution: '[Worklets] Native part of Worklets doesn't seem to be initialized.'

[nmehlei]

After upgrading:

• react-native from 0.82.1 -> 0.83.0
• react-native-reanimated from 4.1.5 -> 4.2.1
• react-native-worklets from 0.6.1 -> 0.7.1
  the following error happens for all my unit tests

    Test suite failed to run

    WorkletsError: [Worklets] Native part of Worklets doesn't seem to be initialized.
    See https://docs.swmansion.com/react-native-worklets/docs/guides/troubleshooting#native-part-of-worklets-doesnt-seem-to-be-initialized for more details.

      37 |
    > 38 | require('react-native-reanimated').setUpTests();
         | ^
      39 |

      at new WorkletsErrorConstructor (node_modules/react-native-worklets/src/debug/WorkletsError.native.ts:14:25)
      at new NativeWorklets (node_modules/react-native-worklets/src/WorkletsModule/NativeWorklets.native.ts:31:13)
      at Object.<anonymous> (node_modules/react-native-worklets/src/WorkletsModule/NativeWorklets.native.ts:275:48)
      at Object.require (node_modules/react-native-worklets/src/memory/serializable.native.ts:10:1)
      at Object.require (node_modules/react-native-worklets/src/memory/synchronizableUnpacker.native.ts:3:1)
      at Object.require (node_modules/react-native-worklets/src/initializers/initializers.native.ts:8:1)
      at Object.require (node_modules/react-native-worklets/src/index.ts:3:1)
      at Object.require (node_modules/react-native-reanimated/src/initializers.ts:2:1)
      at Object.require (node_modules/react-native-reanimated/src/index.ts:5:1)
      at Object.require (jest/setup.js:38:1)

The execution breaks at the jest setup code, which is set up as documented here:
require('react-native-reanimated').setUpTests();

The actual app execution seems to be fine, so the issue is isolated to Jest-based unit tests.

What could be the cause of this?

[MatiPl01]

Hey! Please try adding this to your jest setup file:

jest.mock('react-native-worklets', () =>
  require('react-native-worklets/src/mock')
);

I wonder if we have this documented anywhere. If not, we will add this to docs.

[nmehlei]

Ah thank you, that's helpful. I don't think that's actually documented. I would have expected it at least here: https://docs.swmansion.com/react-native-reanimated/docs/guides/testing

Unfortunately, it did not completely solve the issue for me. While worklets are being initialized now (or at least the mocks are), I'm now getting the following error for all unit tests exclusively which make use of react-native-reanimated: Too many re-renders. React limits the number of renders to prevent an infinite loop.

Running the app itself or downgrading to the earlier versions work.

[MatiPl01]

Can you check which library is causing the issue? If you downgrade reanimated and worklets it works fine or you have to downgrade react native as well to make it work?

[tjzel]

@nmehlei Recently I fixes some Jest issues with Worklets and Reanimated. Could you check if it still reproduces with react-native-reanimated@nightly and react-native-worklets@nightly?