Cannot find name 'describe'. Do you need to install type definitions for a test runner?

I'm using VSCode as my IDE and in my Angular project, I had to comment-out/remove types in tsconfig.json and add jest in types at tsconfig.spec.json.

tsconfig.json

{
  "compilerOptions": {
    // "types": []
  }
}

tsconfig.spec.json

{
  "compilerOptions": {
    "types": ["jest", "node"]
  }
}

It's a bit tricky one because both: your IDE (i.e. VSCode) and TypeScript use tsconfig.json for their own purpose.

Simple checklist to solve the initial problem:

(for TypeScript and Jest)

1. Make sure you have @types/jest and @types/node installed.
2. Make sure you have linked these types in tsconfig.json so that: types: ["jest", "node"]
3. Make sure you don't have your tests or the tests directory excluded from tsconfig.json configuration in excluded property.

Side-effect on transpilation

If you transpile from TypeScript to JavaScript using tsc or any custom module that relies on tsconfig.json then you may notice that your tests will be transpiled too in such case (you'll see their .js correspondence in your build directory).

However, in most of the cases you will have either:

1. separate tsconfig.prod.json with configuration that overwrites the default one. There are many settings like inlineSource, sourceMaps, inlineSourceMaps which you'd probably want to disable too and then use tsc --project tsconfig.prod.json to build
2. terminal (npm/yarn script) command that overwrites the default config with the specific flags. Example: npx tsc --inlineSourceMap false --declarationMap false --inlineSources false --sourceMap false. At that point you can use --excludeFiles or --excludeDirectories flag to exclude your tests from the build as per documentation.

The alternative is to use package like rimraf and delete unnecessary files as a part of the build process. Might be less complex than overwriting the configuration and easier to maintain as a build step. In such case you may use the command: yarn rimraf build/**/*.test.js

None of the above fixed my issue. I had to add "@types/jest" to the types array in the tsconfig.json file.

This worked for me:

import '@types/jest';