wp-calypso/docs/testing/faq.md

FAQ

What tools and libraries are used?

We use Jest testing tool to execute all test configurations located in Calypso repository. It's highly recommended to use Jest's very flexible API together with expect matchers and mock functions.

Historically we have been using Mocha with Chai assertions and Sinon mocks. We no longer support Chai and Sinon, so Jest equivalents must be used whenever new tests are added.

End-to-end tests use Playwright to interact with the browser, and Jest to write and drive the testing scripts.

How to run all tests?

Executing yarn test from the root folder will run all test suites. Behind the scenes we maintain 3 test configuration. This is because each of them (client, server, and integration) has their own requirements.

How to run a smaller subset of test files?

We have a yarn run script for each tests type: yarn run test-client, yarn run test-server, yarn run test-integration. You can pass a filename, folder name or matching pattern to these scripts to narrow down number of executed tests.

Example for client:

> # run test suite for a specific test file
> yarn run test-client client/state/selectors/test/get-media.js
> # run test suites for all files in a specific folder
> yarn run test-server server/config
> # run test suites for all files matching pattern
> yarn run test-client client/*/domains

How to run specified suite or test-case

The exclusivity feature allows you to run only the specified suite or test-case by appending .only() to the function. It works with describe and it functions. More details in Jest documentation.

Using only is a little bit dangerous, as you may end up committing the only, which would cause the test suite to only run your test on the build server. So be sure to look for stray only calls when reviewing a test. We have ESLint rules that should catch them for you.

Example:

describe.only( 'just run this suite', function () {
    test( 'should run these tests', function () {
        // your test
    } );

    test.only( 'should only run this one test', function () {
        // just run this test if the only is present
    } );
} );