woocommerce/tests/framework/class-wc-rest-unit-test-case.php

<?php
/**
 * WC REST API Unit Test Case (for WP-API Endpoints).
 *
 * Provides REST API specific methods and setup/teardown.
 *
 * @since 3.0
 */

 class WC_REST_Unit_Test_Case extends WC_Unit_Test_Case {

     protected $server;

    /**
     * Setup our test server.
     */
    public function setUp() {
        parent::setUp();
        global $wp_rest_server;
        $this->server = $wp_rest_server = new WP_Test_Spy_REST_Server;
        do_action( 'rest_api_init' );
    }

    /**
     * Unset the server.
     */
    public function tearDown() {
        parent::tearDown();
		global $wp_rest_server;
		unset( $this->server );
        $wp_rest_server = null;
    }
}