### Version 3.0.0-alpha.8 ### Reproduction link [https://have.not](https://have.not) ### Steps to reproduce Check generated runtime-test.d.ts ### What is expected? [Jest type extension](https://github.com/vuejs/vue-next/blob/master/packages/runtime-test/src/utils/mockWarn.ts#L1) should be included in `runtime-test.d.ts`. ### What is actually happening? It's not. --- I think it's an [api-extractor](https://github.com/microsoft/rushstack/tree/master/apps/api-extractor) bug. Related issue: https://github.com/microsoft/rushstack/issues/1709 <!-- generated by vue-issues. DO NOT REMOVE -->