Implement tests for type definitions in Jest

[SaurabhAgarwala]

Summary

Related to #8794

This PR adds type definitions tests for Jest's own API. The types are imported from @jest/types and @jest/globals. The tests for foo are defined in a file call foo.test.ts present in the test-types directory under the root directory.

A custom runner called jest-runner-tsd is being used for the type definition tests.

Under the hood, a forked version of tsd is being used for carrying out the tests.

This PR implements the type testing feature. More type tests for other Jest APIs will be added as a separate PR.

Demo

The above screenshot demonstrate the working of both the failing as well as passing type tests for a few API of the top-level-jest-namespace. The failing tests are just for demo purpose and will be deleted once the PR is approved.

Authors

• Co-authored-by: Karan Sanjeev Nair < [email protected] >
• Co-authored-by: Saurabh Agarwala < [email protected] >

[SimenB]

We only emit the TS types for the Running TypeScript compiler & ESLint workflow, so I believe we need to only run the type tests in that workflow as well. A separate config file might be what we wanna do rather than using projects here.

// jest.config.types.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

'use strict';

module.exports = {
  displayName: 'typings test',
  runner: 'jest-runner-tsd',
  testMatch: ['<rootDir>/test-types/*.test.ts'],
};

then add a script for running it

{
  "scripts": {
    "test-types": "yarn jest --config jest.config.types.js"
  }
}

and finally in the workflow after this: https://github.com/facebook/jest/blob/c9c8dba4dd8de34269bdb971173659399bcbfd55/.github/workflows/nodejs.yml#L40-L41

[SimenB]

can we do something like this to make it be more "typescript color" than green?

Suggested change

	displayName: 'typings test',
	displayName: {
	color: 'blue',
	name: 'types',
	},

[SimenB]

👏

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