Limit use of realTimers to Jest's fakeTimers #652
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A recent change to `runWithRealTimers` added a check for the `clock` attribute on `setTimeout` so that we can determine whether timers were faked with Jest's modern fake timers (which are based on `@sinonjs/fake-timers`). Unfortunately, this attribute can be present when users are not using Jest's fake timers and are using sinonjs. Also, when `useFakeTimers` are invoked without parameters in Jest 26, the legacy timers are used by default. This PR addresses two issues: 1. Don't use realTimers if the timers were not faked by Jest. 2. If we're using realTimers, make sure we're explicit when calling `useFakeTimers` so that the fakes are restored to their original state.
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🎉 This PR is included in version 7.16.2 🎉 The release is available on:
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Thanks @kentcdodds, feels good to have contributed. |
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@all-contributors please add @kgregory for code and tests |
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I've put up a pull request to add @kgregory! 🎉 |
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Thanks so much for your help! I've added you as a collaborator on the project. Please make sure that you review the |
What:
Modify
runWithRealTimersso that real timers are only used if they were faked by Jest's legacy or modern implementation of fake timers.Also, when restoring Jest's fakes, be explicit in specifying whether we're restoring the
modernorlegacyfakes.Why:
A recent change to
runWithRealTimersadded a check for theclockattribute onsetTimeoutso that we can determine whether timers were faked with Jest's modern fake timers (which are based on@sinonjs/fake-timers). See issue thread.Unfortunately, this attribute can be present when users are not using Jest's fake timers and are using sinonjs. Also, when
useFakeTimersare invoked without parameters in Jest 26, the legacy timers are used by default.How:
Determine if Jest legacy timers are used by checking
globalObj.setTimeout._isMockFunction.Determine if Jest modern timers are used by checking for the presence of
globalObj.setTimeout.clockand also by verifying that use ofjest.getRealSystemTimeis supported. It was introduced in Jest 26 and is only available when modern fake timers are used.Checklist:
docs site