![](\"https://jestjs.io/img/jest.png\")
\n ![](\"https://jestjs.io/img/circus.png\")
\n \n \n jest-circus
\nThe next-gen test runner for Jest
\n\n\n## Overview\n\nCircus is a flux-based test runner for Jest that is fast, maintainable, and simple to extend.\n\nCircus allows you to bind to events via an optional event handler on any [custom environment](https://jestjs.io/docs/configuration#testenvironment-string). See the [type definitions][type-definitions] for more information on the events and state data currently available.\n\n```js\nimport {Event, State} from 'jest-circus';\nimport NodeEnvironment from 'jest-environment-node';\n\nclass MyCustomEnvironment extends NodeEnvironment {\n //...\n\n async handleTestEvent(event: Event, state: State) {\n if (event.name === 'test_start') {\n // ...\n }\n }\n}\n```\n\nMutating event or state data is currently unsupported and may cause unexpected behavior or break in a future release without warning. New events, event data, and/or state data will not be considered a breaking change and may be added in any minor release.\n\nNote, that `jest-circus` test runner would pause until a promise returned from `handleTestEvent` gets fulfilled. **However, there are a few events that do not conform to this rule, namely**: `start_describe_definition`, `finish_describe_definition`, `add_hook`, `add_test` or `error` (for the up-to-date list you can look at [SyncEvent type in the types definitions][type-definitions]). That is caused by backward compatibility reasons and `process.on('unhandledRejection', callback)` signature, but that usually should not be a problem for most of the use cases.\n\n## Installation\n\n> Note: As of Jest 27, `jest-circus` is the default test runner, so you do not have to install it to use it.\n\nInstall `jest-circus` using yarn:\n\n```bash\nyarn add --dev jest-circus\n```\n\nOr via npm:\n\n```bash\nnpm install --save-dev jest-circus\n```\n\n## Configure\n\nConfigure Jest to use `jest-circus` via the [`testRunner`](https://jestjs.io/docs/configuration#testrunner-string) option:\n\n```json\n{\n \"testRunner\": \"jest-circus/runner\"\n}\n```\n\nOr via CLI:\n\n```bash\njest --testRunner='jest-circus/runner'\n```\n", "description": "Circus is a flux-based test runner for Jest that is fast, maintainable, and simple to extend.", "licenseText": "MIT License\n\nCopyright (c) Facebook, Inc. and its affiliates.\n\nPermission is hereby granted, free of charge, to any person obtaining a copy\nof this software and associated documentation files (the \"Software\"), to deal\nin the Software without restriction, including without limitation the rights\nto use, copy, modify, merge, publish, distribute, sublicense, and/or sell\ncopies of the Software, and to permit persons to whom the Software is\nfurnished to do so, subject to the following conditions:\n\nThe above copyright notice and this permission notice shall be included in all\ncopies or substantial portions of the Software.\n\nTHE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR\nIMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,\nFITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE\nAUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER\nLIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,\nOUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE\nSOFTWARE.\n" }, "artifacts": [], "remote": { "resolved": "https://registry.yarnpkg.com/jest-circus/-/jest-circus-27.5.1.tgz#37a5a4459b7bf4406e53d637b49d22c65d125ecc", "type": "tarball", "reference": "https://registry.yarnpkg.com/jest-circus/-/jest-circus-27.5.1.tgz", "hash": "37a5a4459b7bf4406e53d637b49d22c65d125ecc", "integrity": "sha512-D95R7x5UtlMA5iBYsOHFFbMD/GVA4R/Kdq15f7xYWUfWHBto9NYRsOvnSauTgdF+ogCpJ4tyKOXhUifxS65gdw==", "registry": "npm", "packageName": "jest-circus", "cacheIntegrity": "sha512-D95R7x5UtlMA5iBYsOHFFbMD/GVA4R/Kdq15f7xYWUfWHBto9NYRsOvnSauTgdF+ogCpJ4tyKOXhUifxS65gdw== sha1-N6WkRZt79EBuU9Y3tJ0ixl0SXsw=" }, "registry": "npm", "hash": "37a5a4459b7bf4406e53d637b49d22c65d125ecc" }