source: trunk/tests/phpunit/includes/spy-rest-server.php

<?php

class Spy_REST_Server extends WP_REST_Server {

        public $sent_headers        = array();
        public $sent_body           = '';
        public $last_request        = null;
        public $override_by_default = false;
        public $status              = null;

        /**
         * Gets the raw $endpoints data from the server.
         *
         * @return array
         */
        public function get_raw_endpoint_data() {
                return $this->endpoints;
        }

        /**
         * Allow calling protected methods from tests.
         *
         * @param string $method Method to call.
         * @param array  $args   Arguments to pass to the method.
         * @return mixed
         */
        public function __call( $method, $args ) {
                if ( ! method_exists( $this, $method ) ) {
                        throw new Error( sprintf( 'Call to undefined method %s::%s()', get_class( $this ), $method ) );
                }

                return call_user_func_array( array( $this, $method ), $args );
        }

        /**
         * Adds a header to the list of sent headers.
         *
         * @param string $header Header name.
         * @param string $value  Header value.
         */
        public function send_header( $header, $value ) {
                $this->sent_headers[ $header ] = $value;
        }

        /**
         * Removes a header from the list of sent headers.
         *
         * @param string $header Header name.
         */
        public function remove_header( $header ) {
                unset( $this->sent_headers[ $header ] );
        }

        /**
         * Stores last set status.
         *
         * @param int $status HTTP status.
         */
        public function set_status( $status ) {
                $this->status = $status;
        }

        /**
         * Overrides the dispatch method so we can get a handle on the request object.
         *
         * @param  WP_REST_Request $request Request to attempt dispatching.
         * @return WP_REST_Response Response returned by the callback.
         */
        public function dispatch( $request ) {
                $this->last_request = $request;
                return parent::dispatch( $request );
        }

        /**
         * Overrides the register_route method so we can re-register routes internally if needed.
         *
         * @param string $route_namespace Namespace.
         * @param string $route           The REST route.
         * @param array  $route_args      Route arguments.
         * @param bool   $override        Optional. Whether the route should be overridden if it already exists.
         *                                Default false. Also set `$GLOBALS['wp_rest_server']->override_by_default = true`
         *                                to set overrides when you don't have access to the caller context.
         */
        public function register_route( $route_namespace, $route, $route_args, $override = false ) {
                parent::register_route( $route_namespace, $route, $route_args, $override || $this->override_by_default );
        }

        /**
         * Serves the request and returns the result.
         *
         * @param string $path Optional. The request route. If not set, `$_SERVER['PATH_INFO']` will be used.
         *                     Default null.
         * @return null|false Null if not served and a HEAD request, false otherwise.
         */
        public function serve_request( $path = null ) {

                ob_start();
                $result          = parent::serve_request( $path );
                $this->sent_body = ob_get_clean();
                return $result;
        }
}