jest-runner-tsd

jest-runner-tsd

A Jest runner that tests typescript typings using tsd under the hood.

Install

Install jest-runner-tsd

yarn add --dev jest-runner-tsd

# or with NPM

npm install --save-dev jest-runner-tsd

Adding to Jest Config

Create a jest.config.types.js file and have the runner property set to jest-runner-tsd as shown below:

module.exports = {
  runner: 'jest-runner-tsd',
};

In the project package.json file, modify the scripts block to use the configuration file as show below:

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

Run

To start the test, just execute the following command

yarn test-types

Writing tests

This runner uses TSD. To see the available assertions, checkout it's documentation

For JavaScript Projects

There are multiple ways you can pass a type definition file.

Default

The type definitions should be in a file named index.d.ts in the root directory of the project by default.

types property in package.json

You can also set your types property in package.json. The runner will automatically pick the type defintion file from there.

{
  ...
  "types": "path/to/types.d.ts"
}

Docblocks

If the type definition file is located somewhere else then specify its path in the top of respective test file using the @type inside a docblock.

/**
 * @type ../../custom/path/to/types.d.ts
 **/

For TypeScript Projects

Note: This is only a workaround. A stable solution may be introduced in future.

Due to limitations in TSD, the only solution now for testing types in TypeScript projects would be to have a empty type definition file and specify it's path using one of the many methods explained above.