title: Cannot find name 'describe'. Do you need to install type definitions for a test runner?
body: <p>When using TypeScript in conjunction with Jest, my specs would fail with error messages like:</p>
  
  <pre><code>test/unit/some.spec.ts:1:1 - error TS2582: Cannot find name 'describe'. Do you need to install type definitions for a test runner? Try `npm i @types/jest` or `npm i @types/mocha`.
  test/unit/some.spec.ts:2:3 - error TS2582: Cannot find name 'it'. Do you need to install type definitions for a test runner? Try `npm i @types/jest` or `npm i @types/mocha`.
  test/unit/some.spec.ts:3:7 - error TS2304: Cannot find name 'expect'.
  test/unit/some.spec.ts:7:1 - error TS2582: Cannot find name 'test'. Do you need to install type definitions for a test runner? Try `npm i @types/jest` or `npm i @types/mocha`.
  </code></pre>
  
  <p>The types are already installed.</p>
  
  <p>I use:</p>
  
  <pre><code>    "@types/jest": "^23.3.12",
      "jest": "^23.6.0",
      "ts-jest": "^23.10.5",
      "typescript": "^3.1.6"
  </code></pre>
  
  <p>I run tests using <code>jest --forceExit --coverage --verbose</code></p>