add FakeHttpClient

tests/phpunit/includes/FakeHttpClient.php

@@ -0,0 +1,49 @@
+<?php
+/**
+ * Fake HTTP Client
+ *
+ * @package   Google\Site_Kit\Tests
+ * @copyright 2019 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ * @link      https://sitekit.withgoogle.com
+ */
+
+namespace Google\Site_Kit\Tests;
+
+use Google\Site_Kit_Dependencies\GuzzleHttp\Client;
+use Google\Site_Kit_Dependencies\GuzzleHttp\Message\RequestInterface;
+use Google\Site_Kit_Dependencies\GuzzleHttp\Message\Response;
+
+/**
+ * Class FakeHttpClient
+ */
+class FakeHttpClient extends Client {
+	/**
+	 * Handler function for overriding requests.
+	 *
+	 * @var callable
+	 */
+	protected $request_handler;
+
+	/**
+	 * Sets the handler for all requests.
+	 *
+	 * @param callable $handler
+	 */
+	public function set_request_handler( callable $handler ) {
+		$this->request_handler = $handler;
+	}
+
+	/**
+	 * @param RequestInterface $request
+	 *
+	 * @return \Google\Site_Kit_Dependencies\GuzzleHttp\Message\ResponseInterface
+	 */
+	public function send( RequestInterface $request ) {
+		if ( $this->request_handler ) {
+			return call_user_func( $this->request_handler, $request );
+		}
+
+		return new Response( 200 );
+	}
+}