{"id":"7be8508e88cf2206","repo":"jestjs/jest","slug":"missing-method-createworker-in-workerpool","errorCode":null,"errorMessage":"Missing method createWorker in WorkerPool","messagePattern":"Missing method createWorker in WorkerPool","errorType":"exception","errorClass":"Error","httpStatus":null,"severity":"error","filePath":"packages/jest-worker/src/base/BaseWorkerPool.ts","lineNumber":105,"sourceCode":"    if (this._workers[workerId].state === WorkerStates.SHUT_DOWN) {\n      const {forkOptions, maxRetries, resourceLimits, setupArgs} =\n        this._options;\n      const workerOptions: WorkerOptions = {\n        forkOptions,\n        idleMemoryLimit: this._options.idleMemoryLimit,\n        maxRetries,\n        resourceLimits,\n        setupArgs,\n        workerId,\n        workerPath: this._workerPath,\n      };\n      const worker = this.createWorker(workerOptions);\n      this._workers[workerId] = worker;\n    }\n  }\n\n  createWorker(_workerOptions: WorkerOptions): WorkerInterface {\n    throw new Error('Missing method createWorker in WorkerPool');\n  }\n\n  async start(): Promise<void> {\n    await Promise.all(\n      this._workers.map(async worker => {\n        await worker.waitForWorkerReady();\n\n        await new Promise<void>((resolve, reject) => {\n          worker.send(\n            [CHILD_MESSAGE_CALL_SETUP],\n            emptyMethod,\n            error => {\n              if (error) {\n                reject(error);\n              } else {\n                resolve();\n              }\n            },","sourceCodeStart":87,"sourceCodeEnd":123,"githubUrl":"https://github.com/jestjs/jest/blob/f49721c78e195558b40913977c9230f5b7f559d8/packages/jest-worker/src/base/BaseWorkerPool.ts#L87-L123","documentation":"Error \"Missing method createWorker in WorkerPool\" thrown in jestjs/jest.","triggerScenarios":"Thrown at packages/jest-worker/src/base/BaseWorkerPool.ts:105 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["This is an internal Jest bug: a custom WorkerPool implementation must define a createWorker method. If you subclass BaseWorkerPool, implement createWorker() and return a ChildProcessWorker or NodeThreadsWorker instance.","If you are not extending jest-worker yourself, upgrade Jest to the latest version and report the issue to the Jest repository."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"analyzedSha":"f49721c78e195558b40913977c9230f5b7f559d8","analyzedAt":"2026-08-03T20:16:28.571Z","schemaVersion":2}