diff --git a/Tests/FactoryTest.php b/Tests/FactoryTest.php
new file mode 100644
index 0000000..cb59cf1
--- /dev/null
+++ b/Tests/FactoryTest.php
@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * This file is part of the PHPFUI\ConstantContact package
+ *
+ * (c) Bruce Wells
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source
+ * code
+ */
+class FactoryTest extends \PHPUnit\Framework\TestCase
+	{
+	public function testSetFactory() : void
+		{
+		$this->assertNull(\PHPFUI\ConstantContact\Client::getGuzzleFactory());
+		$callable = [GrahamCampbell\GuzzleFactory\GuzzleFactory::class, 'make'];
+		\PHPFUI\ConstantContact\Client::setGuzzleFactory($callable);
+		$this->assertEquals($callable, \PHPFUI\ConstantContact\Client::getGuzzleFactory());
+		\PHPFUI\ConstantContact\Client::setGuzzleFactory(null);
+		$client = new \PHPFUI\ConstantContact\Client('clientAPIKey', 'clientSecret', 'redirectURI');
+		$guzzle = $client->getGuzzleClient('body', ['header1' => 'HEADER1']);
+		$this->assertTrue($guzzle instanceof \GuzzleHttp\Client);
+		$config = $guzzle->getConfig('body');
+		$this->assertEquals('body', $config);
+		$config = $guzzle->getConfig('headers');
+		$this->assertIsArray($config);
+		$this->assertArrayHasKey('header1', $config);
+		$this->assertContains('HEADER1', $config);
+		$this->assertArrayHasKey('Cache-Control', $config);
+		\PHPFUI\ConstantContact\Client::setGuzzleFactory($callable);
+		$guzzle = $client->getGuzzleClient('body', ['header1' => 'HEADER1']);
+		$this->assertTrue($guzzle instanceof \GuzzleHttp\Client);
+		$config = $guzzle->getConfig('body');
+		$this->assertEquals('body', $config);
+		$config = $guzzle->getConfig('headers');
+		$this->assertIsArray($config);
+		$this->assertArrayHasKey('header1', $config);
+		$this->assertContains('HEADER1', $config);
+		$this->assertArrayHasKey('Cache-Control', $config);
+		}
+	}
diff --git a/Tests/HydrateTest.php b/Tests/HydrateTest.php
index 05195ca..9200045 100644
--- a/Tests/HydrateTest.php
+++ b/Tests/HydrateTest.php
@@ -67,8 +67,8 @@ public function testHydration() : void
 		$this->assertEquals('xxxx@mailinator.com', $contacts->contacts[0]->email_address->address);
 		$this->assertEquals('xxxx@mailinator.com', $contacts->contacts[1]->email_address->address);
 		$time = new \PHPFUI\ConstantContact\DateTime("2024-11-08T10:54:32Z");
-		$this->assertEquals("{$time}", "{$contacts->contacts[0]->created_at}");
-		$this->assertEquals("{$time}", "{$contacts->contacts[1]->created_at}");
+		$this->assertEquals((string)$time, (string)$contacts->contacts[0]->created_at);
+		$this->assertEquals((string)$time, (string)$contacts->contacts[1]->created_at);
 		$newJson = $contacts->getJSON();
 		$this->assertJson($newJson);
 		$newDataArray = $contacts->toArray();
diff --git a/composer.json b/composer.json
index 0a810d0..f2ef839 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,8 @@
         "roave/security-advisories": "dev-latest",
         "friendsofphp/php-cs-fixer": "^3.0",
         "symfony/yaml": "^7.0",
-        "phpstan/phpstan": "^2.0"
+        "phpstan/phpstan": "^2.0",
+        "graham-campbell/guzzle-factory": "^7.0"
     },
     "autoload": {
         "psr-4": {"PHPFUI\\ConstantContact\\": "src/ConstantContact/"}
diff --git a/src/ConstantContact/Client.php b/src/ConstantContact/Client.php
index fb8f105..db2c4e3 100644
--- a/src/ConstantContact/Client.php
+++ b/src/ConstantContact/Client.php
@@ -20,6 +20,8 @@ class Client
 
 	private string $body = '';
 
+	private static $guzzleFactory = null;
+
 	private \GuzzleHttp\HandlerStack $guzzleHandler;
 
 	private string $host = '';
@@ -124,8 +126,7 @@ public function delete(string $url) : ?array
 		{
 		try
 			{
-			$guzzle = new \GuzzleHttp\Client(['headers' => $this->getHeaders(), 'handler' => $this->guzzleHandler, ]);
-			$response = $guzzle->request('DELETE', $url);
+			$response = $this->getGuzzleClient()->request('DELETE', $url);
 
 			return $this->process($response);
 			}
@@ -156,8 +157,7 @@ public function get(string $url, array $parameters) : ?array
 					}
 				}
 
-			$guzzle = new \GuzzleHttp\Client(['headers' => $this->getHeaders(), 'handler' => $this->guzzleHandler, ]);
-			$response = $guzzle->request('GET', $url);
+			$response = $this->getGuzzleClient()->request('GET', $url);
 
 			return $this->process($response);
 			}
@@ -213,11 +213,35 @@ public function getBody() : string
 		return $this->body;
 		}
 
+	public function getGuzzleClient(string $body = '', array $headers = []) : \GuzzleHttp\Client
+		{
+		$config = [
+			'headers' => $this->getHeaders($headers),
+			'handler' => $this->guzzleHandler, ];
+
+		if (\strlen($body))
+			{
+			$config['body'] = $body;
+			}
+
+		return self::$guzzleFactory ? \call_user_func(self::$guzzleFactory, $config) : new \GuzzleHttp\Client($config);
+		}
+
+	public static function getGuzzleFactory() : ?callable
+		{
+		return self::$guzzleFactory;
+		}
+
 	public function getLastError() : string
 		{
 		return $this->lastError;
 		}
 
+	public function getSessionCallback() : ?callable
+		{
+		return $this->sessionCallback;
+		}
+
 	public function getStatusCode() : int
 		{
 		return $this->statusCode;
@@ -235,8 +259,7 @@ public function next() : array
 			return [];
 			}
 
-		$guzzle = new \GuzzleHttp\Client(['headers' => $this->getHeaders(), 'handler' => $this->guzzleHandler, ]);
-		$response = $guzzle->request('GET', 'https://api.cc.email' . $this->next);
+		$response = $this->getGuzzleClient()->request('GET', 'https://api.cc.email' . $this->next);
 
 		return $this->process($response);
 		}
@@ -257,10 +280,7 @@ public function post(string $url, array $parameters) : ?array
 		try
 			{
 			$json = \json_encode($parameters['body'], JSON_PRETTY_PRINT);
-			$guzzle = new \GuzzleHttp\Client(['headers' => $this->getHeaders(),
-				'handler' => $this->guzzleHandler,
-				'body' => $json, ]);
-			$response = $guzzle->request('POST', $url);
+			$response = $this->getGuzzleClient()->request('POST', $url);
 
 			return $this->process($response);
 			}
@@ -281,7 +301,8 @@ public function put(string $url, array $parameters, string $method = 'PUT') : ?a
 		try
 			{
 			$json = \json_encode($parameters['body'], JSON_PRETTY_PRINT);
-			$guzzle = new \GuzzleHttp\Client(['headers' => $this->getHeaders(
+			$guzzle = $this->getGuzzleClient(
+				$json,
 				[
 					'Connection' => 'keep-alive',
 					'Content-Length' => \strlen($json),
@@ -289,10 +310,7 @@ public function put(string $url, array $parameters, string $method = 'PUT') : ?a
 					'Host' => $this->host,
 					'Accept' => '*/*'
 				]
-			),
-				'handler' => $this->guzzleHandler,
-				'body' => $json, ]);
-
+			);
 			$response = $guzzle->request($method, $url);
 
 			return $this->process($response);
@@ -341,6 +359,11 @@ public function removeScope(string $scope) : self
 		return $this;
 		}
 
+	public static function setGuzzleFactory(?callable $factory) : void
+		{
+		self::$guzzleFactory = $factory;
+		}
+
 	public function setHost(string $host) : self
 		{
 		$this->host = $host;