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Add actionable message for "React.act is not a function" error #1439

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Add actionable message for "React.act is not a function" error #1439

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74512bb
Add actionable message for "React.act is not a function" error
andrzejressel Jan 1, 2026
66cfb82
Add check for Error.isError
andrzejressel Jan 1, 2026
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15 changes: 15 additions & 0 deletions src/act-compat.js
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,21 @@ function withGlobalActEnvironment(actImplementation) {
return actResult
}
} catch (error) {
// https://github.com/testing-library/react-testing-library/issues/1392
// https://github.com/testing-library/react-testing-library/issues/1399
if (
// Error.isError is pretty new addition to Node.js - may not be available in LTS versions
Error.isError &&
Error.isError(error) &&
error.toString() === 'TypeError: React.act is not a function' &&
process &&
process.env.NODE_ENV === 'production'
) {
throw new Error(
'Following error may be caused by `NODE_ENV` environment variable being set to `production`. Try changing it to `test`.',
{cause: error},
)
}
// Can't be a `finally {}` block since we don't know if we have to immediately restore IS_REACT_ACT_ENVIRONMENT
// or if we have to await the callback first.
setIsReactActEnvironment(previousActEnvironment)
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