wp-calypso/test/server/setup-test-framework.js

import * as nock from 'nock';

// Disables all network requests for all tests.
nock.disableNetConnect();

beforeAll( () => {
	// reactivate nock on test start
	if ( ! nock.isActive() ) {
		nock.activate();
	}
} );

afterAll( () => {
	// helps clean up nock after each test run and avoid memory leaks
	nock.restore();
	nock.cleanAll();
} );

// Don't need to mock specific functions for any tests, but mocking
// module because it accesses the `document` global.
jest.mock( 'wpcom-proxy-request', () => ( {
	__esModule: true,
} ) );