diff --git a/src/Mailgun/Api/Domain.php b/src/Mailgun/Api/Domain.php
index 27aa4e0..8954ace 100644
--- a/src/Mailgun/Api/Domain.php
+++ b/src/Mailgun/Api/Domain.php
@@ -10,15 +10,15 @@
 namespace Mailgun\Api;
 
 use Mailgun\Assert;
+use Mailgun\Resource\Api\Domain\ConnectionResponse;
 use Mailgun\Resource\Api\Domain\CreateCredentialResponse;
 use Mailgun\Resource\Api\Domain\CreateResponse;
+use Mailgun\Resource\Api\Domain\CredentialResponse;
 use Mailgun\Resource\Api\Domain\DeleteCredentialResponse;
 use Mailgun\Resource\Api\Domain\DeleteResponse;
-use Mailgun\Resource\Api\Domain\ShowResponse;
-use Mailgun\Resource\Api\Domain\CredentialResponse;
-use Mailgun\Resource\Api\Domain\ConnectionResponse;
-use Mailgun\Resource\Api\Domain\UpdateConnectionResponse;
 use Mailgun\Resource\Api\Domain\IndexResponse;
+use Mailgun\Resource\Api\Domain\ShowResponse;
+use Mailgun\Resource\Api\Domain\UpdateConnectionResponse;
 use Mailgun\Resource\Api\Domain\UpdateCredentialResponse;
 use Psr\Http\Message\ResponseInterface;
 
@@ -49,7 +49,7 @@ class Domain extends HttpApi
 
         $response = $this->httpGet('/v3/domains', $params);
 
-        return $this->serializer->deserialize($response, IndexResponse::class);
+        return $this->deserializer->deserialize($response, IndexResponse::class);
     }
 
     /**
@@ -65,7 +65,7 @@ class Domain extends HttpApi
 
         $response = $this->httpGet(sprintf('/v3/domains/%s', $domain));
 
-        return $this->serializer->deserialize($response, ShowResponse::class);
+        return $this->deserializer->deserialize($response, ShowResponse::class);
     }
 
     /**
@@ -95,7 +95,7 @@ class Domain extends HttpApi
             'wildcard' => $wildcard,
         ];
 
-        $response = $this->postMultipart('/v3/domains', $params);
+        $response = $this->httpPostMultipart('/v3/domains', $params);
 
         return $this->safeDeserialize($response, CreateResponse::class);
     }
@@ -114,7 +114,7 @@ class Domain extends HttpApi
 
         $response = $this->httpDelete(sprintf('/v3/domains/%s', $domain));
 
-        return $this->serializer->deserialize($response, DeleteResponse::class);
+        return $this->deserializer->deserialize($response, DeleteResponse::class);
     }
 
     /**
@@ -163,9 +163,9 @@ class Domain extends HttpApi
             'password' => $password,
         ];
 
-        $response = $this->postMultipart(sprintf('/v3/domains/%s/credentials', $domain), $params);
+        $response = $this->httpPostMultipart(sprintf('/v3/domains/%s/credentials', $domain), $params);
 
-        return $this->serializer->deserialize($response, CreateCredentialResponse::class);
+        return $this->deserializer->deserialize($response, CreateCredentialResponse::class);
     }
 
     /**
@@ -188,7 +188,7 @@ class Domain extends HttpApi
             'password' => $pass,
         ];
 
-        $response = $this->putMultipart(
+        $response = $this->httpPutMultipart(
             sprintf(
                 '/v3/domains/%s/credentials/%s',
                 $domain,
@@ -197,7 +197,7 @@ class Domain extends HttpApi
             $params
         );
 
-        return $this->serializer->deserialize($response, UpdateCredentialResponse::class);
+        return $this->deserializer->deserialize($response, UpdateCredentialResponse::class);
     }
 
     /**
@@ -213,7 +213,7 @@ class Domain extends HttpApi
         Assert::stringNotEmpty($domain);
         Assert::stringNotEmpty($login);
 
-        $response = $this->delete(
+        $response = $this->httpDelete(
             sprintf(
                 '/v3/domains/%s/credentials/%s',
                 $domain,
@@ -221,7 +221,7 @@ class Domain extends HttpApi
             )
         );
 
-        return $this->serializer->deserialize($response, DeleteCredentialResponse::class);
+        return $this->deserializer->deserialize($response, DeleteCredentialResponse::class);
     }
 
     /**
@@ -237,7 +237,7 @@ class Domain extends HttpApi
 
         $response = $this->httpGet(sprintf('/v3/domains/%s/connection', $domain));
 
-        return $this->serializer->deserialize($response, ConnectionResponse::class);
+        return $this->deserializer->deserialize($response, ConnectionResponse::class);
     }
 
     /**
@@ -266,8 +266,8 @@ class Domain extends HttpApi
             $params['skip_verification'] = $noVerify ? 'true' : 'false';
         }
 
-        $response = $this->putMultipart(sprintf('/v3/domains/%s/connection', $domain), $params);
+        $response = $this->httpPutMultipart(sprintf('/v3/domains/%s/connection', $domain), $params);
 
-        return $this->serializer->deserialize($response, UpdateConnectionResponse::class);
+        return $this->deserializer->deserialize($response, UpdateConnectionResponse::class);
     }
 }
diff --git a/src/Mailgun/Api/HttpApi.php b/src/Mailgun/Api/HttpApi.php
index 9c54a03..0aedb33 100644
--- a/src/Mailgun/Api/HttpApi.php
+++ b/src/Mailgun/Api/HttpApi.php
@@ -3,16 +3,16 @@
 namespace Mailgun\Api;
 
 use Http\Client\Common\HttpMethodsClient;
-use Http\Client\HttpClient;
 use Http\Client\Exception as HttplugException;
+use Http\Client\HttpClient;
 use Http\Discovery\MessageFactoryDiscovery;
 use Http\Discovery\StreamFactoryDiscovery;
-use Http\Message\RequestFactory;
 use Http\Message\MultipartStream\MultipartStreamBuilder;
+use Http\Message\RequestFactory;
 use Mailgun\Assert;
+use Mailgun\Deserializer\ResponseDeserializer;
 use Mailgun\Exception\HttpServerException;
-use Mailgun\Serializer\ResponseDeserializer;
-use Mailgun\Resource\Api\SimpleResponse;
+use Mailgun\Resource\Api\ErrorResponse;
 use Psr\Http\Message\ResponseInterface;
 
 /**
@@ -37,10 +37,10 @@ abstract class HttpApi
      * @param RequestFactory       $requestFactory
      * @param ResponseDeserializer $serializer
      */
-    public function __construct(HttpClient $httpClient, RequestFactory $requestFactory, ResponseDeserializer $serializer)
+    public function __construct(HttpClient $httpClient, RequestFactory $requestFactory, ResponseDeserializer $deserializer)
     {
         $this->httpClient = new HttpMethodsClient($httpClient, $requestFactory);
-        $this->serializer = $serializer;
+        $this->deserializer = $deserializer;
     }
 
     /**
@@ -56,9 +56,9 @@ abstract class HttpApi
     protected function safeDeserialize(ResponseInterface $response, $className)
     {
         if ($response->getStatusCode() !== 200) {
-            return $this->serializer->deserialize($response, SimpleResponse::class);
+            return $this->deserializer->deserialize($response, ErrorResponse::class);
         } else {
-            return $this->serializer->deserialize($response, $className);
+            return $this->deserializer->deserialize($response, $className);
         }
     }
 
@@ -109,7 +109,7 @@ abstract class HttpApi
      *
      * @return ResponseInterface
      */
-    protected function postMultipart($path, array $parameters = [], array $requestHeaders = [])
+    protected function httpPostMultipart($path, array $parameters = [], array $requestHeaders = [])
     {
         return $this->doMultipart('POST', $path, $parameters, $requestHeaders);
     }
@@ -163,7 +163,7 @@ abstract class HttpApi
      *
      * @return ResponseInterface
      */
-    protected function putMultipart($path, array $parameters = [], array $requestHeaders = [])
+    protected function httpPutMultipart($path, array $parameters = [], array $requestHeaders = [])
     {
         return $this->doMultipart('PUT', $path, $parameters, $requestHeaders);
     }
@@ -197,7 +197,7 @@ abstract class HttpApi
      *
      * @return ResponseInterface
      */
-    protected function deleteMultipart($path, array $parameters = [], array $requestHeaders = [])
+    protected function httpDeleteMultipart($path, array $parameters = [], array $requestHeaders = [])
     {
         return $this->doMultipart('DELETE', $path, $parameters, $requestHeaders);
     }
diff --git a/src/Mailgun/Api/Stats.php b/src/Mailgun/Api/Stats.php
index 79a2ded..7c14dae 100644
--- a/src/Mailgun/Api/Stats.php
+++ b/src/Mailgun/Api/Stats.php
@@ -25,7 +25,7 @@ class Stats extends HttpApi
 
         $response = $this->httpGet(sprintf('/v3/%s/stats/total', rawurlencode($domain)), $params);
 
-        return $this->serializer->deserialize($response, TotalResponse::class);
+        return $this->deserializer->deserialize($response, TotalResponse::class);
     }
 
     /**
@@ -40,6 +40,6 @@ class Stats extends HttpApi
 
         $response = $this->httpGet(sprintf('/v3/%s/stats', rawurlencode($domain)), $params);
 
-        return $this->serializer->deserialize($response, AllResponse::class);
+        return $this->deserializer->deserialize($response, AllResponse::class);
     }
 }
diff --git a/src/Mailgun/Serializer/ArraySerializer.php b/src/Mailgun/Deserializer/ArrayDeserializer.php
similarity index 61%
rename from src/Mailgun/Serializer/ArraySerializer.php
rename to src/Mailgun/Deserializer/ArrayDeserializer.php
index fe4cf06..0f2889c 100644
--- a/src/Mailgun/Serializer/ArraySerializer.php
+++ b/src/Mailgun/Deserializer/ArrayDeserializer.php
@@ -1,8 +1,8 @@
 <?php
 
-namespace Mailgun\Serializer;
+namespace Mailgun\Deserializer;
 
-use Mailgun\Exception\SerializeException;
+use Mailgun\Exception\DeserializeException;
 use Psr\Http\Message\ResponseInterface;
 
 /**
@@ -10,7 +10,7 @@ use Psr\Http\Message\ResponseInterface;
  *
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
-class ArraySerializer implements ResponseDeserializer
+class ArrayDeserializer implements ResponseDeserializer
 {
     /**
      * @param ResponseInterface $response
@@ -22,12 +22,12 @@ class ArraySerializer implements ResponseDeserializer
     {
         $body = $response->getBody()->__toString();
         if (strpos($response->getHeaderLine('Content-Type'), 'application/json') !== 0) {
-            throw new SerializeException('The ArraySerializer cannot deserialize response with Content-Type:'.$response->getHeaderLine('Content-Type'));
+            throw new DeserializeException('The ArrayDeserializer cannot deserialize response with Content-Type:'.$response->getHeaderLine('Content-Type'));
         }
 
         $content = json_decode($body, true);
         if (JSON_ERROR_NONE !== json_last_error()) {
-            throw new SerializeException(sprintf('Error (%d) when trying to json_decode response', json_last_error()));
+            throw new DeserializeException(sprintf('Error (%d) when trying to json_decode response', json_last_error()));
         }
 
         return $content;
diff --git a/src/Mailgun/Serializer/ModelSerializer.php b/src/Mailgun/Deserializer/ModelDeserializer.php
similarity index 68%
rename from src/Mailgun/Serializer/ModelSerializer.php
rename to src/Mailgun/Deserializer/ModelDeserializer.php
index 7cee2d7..3f3372d 100644
--- a/src/Mailgun/Serializer/ModelSerializer.php
+++ b/src/Mailgun/Deserializer/ModelDeserializer.php
@@ -1,8 +1,8 @@
 <?php
 
-namespace Mailgun\Serializer;
+namespace Mailgun\Deserializer;
 
-use Mailgun\Exception\SerializeException;
+use Mailgun\Exception\DeserializeException;
 use Mailgun\Resource\ApiResponse;
 use Psr\Http\Message\ResponseInterface;
 
@@ -11,7 +11,7 @@ use Psr\Http\Message\ResponseInterface;
  *
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
-class ModelSerializer implements ResponseDeserializer
+class ModelDeserializer implements ResponseDeserializer
 {
     /**
      * @param ResponseInterface $response
@@ -23,12 +23,12 @@ class ModelSerializer implements ResponseDeserializer
     {
         $body = $response->getBody()->__toString();
         if (strpos($response->getHeaderLine('Content-Type'), 'application/json') !== 0) {
-            throw new SerializeException('The ModelSerializer cannot deserialize response with Content-Type:'.$response->getHeaderLine('Content-Type'));
+            throw new DeserializeException('The ModelDeserializer cannot deserialize response with Content-Type:'.$response->getHeaderLine('Content-Type'));
         }
 
         $data = json_decode($body, true);
         if (JSON_ERROR_NONE !== json_last_error()) {
-            throw new SerializeException(sprintf('Error (%d) when trying to json_decode response', json_last_error()));
+            throw new DeserializeException(sprintf('Error (%d) when trying to json_decode response', json_last_error()));
         }
 
         if (is_subclass_of($class, ApiResponse::class)) {
diff --git a/src/Mailgun/Serializer/PSR7Serializer.php b/src/Mailgun/Deserializer/PSR7Deserializer.php
similarity index 82%
rename from src/Mailgun/Serializer/PSR7Serializer.php
rename to src/Mailgun/Deserializer/PSR7Deserializer.php
index 1044750..a8b549d 100644
--- a/src/Mailgun/Serializer/PSR7Serializer.php
+++ b/src/Mailgun/Deserializer/PSR7Deserializer.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Mailgun\Serializer;
+namespace Mailgun\Deserializer;
 
 use Psr\Http\Message\ResponseInterface;
 
@@ -9,7 +9,7 @@ use Psr\Http\Message\ResponseInterface;
  *
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
-class PSR7Serializer implements ResponseDeserializer
+class PSR7Deserializer implements ResponseDeserializer
 {
     /**
      * @param ResponseInterface $response
diff --git a/src/Mailgun/Serializer/ResponseDeserializer.php b/src/Mailgun/Deserializer/ResponseDeserializer.php
similarity index 91%
rename from src/Mailgun/Serializer/ResponseDeserializer.php
rename to src/Mailgun/Deserializer/ResponseDeserializer.php
index a013d7d..f124b69 100644
--- a/src/Mailgun/Serializer/ResponseDeserializer.php
+++ b/src/Mailgun/Deserializer/ResponseDeserializer.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Mailgun\Serializer;
+namespace Mailgun\Deserializer;
 
 use Psr\Http\Message\ResponseInterface;
 
diff --git a/src/Mailgun/Exception/DeserializeException.php b/src/Mailgun/Exception/DeserializeException.php
new file mode 100644
index 0000000..dfc2084
--- /dev/null
+++ b/src/Mailgun/Exception/DeserializeException.php
@@ -0,0 +1,9 @@
+<?php
+
+namespace Mailgun\Exception;
+
+use Mailgun\Exception;
+
+class DeserializeException extends \RuntimeException implements Exception
+{
+}
diff --git a/src/Mailgun/Exception/SerializeException.php b/src/Mailgun/Exception/SerializeException.php
deleted file mode 100644
index da1e200..0000000
--- a/src/Mailgun/Exception/SerializeException.php
+++ /dev/null
@@ -1,9 +0,0 @@
-<?php
-
-namespace Mailgun\Exception;
-
-use Mailgun\Exception;
-
-class SerializeException extends \RuntimeException implements Exception
-{
-}
diff --git a/src/Mailgun/Mailgun.php b/src/Mailgun/Mailgun.php
index 111fb10..22732da 100644
--- a/src/Mailgun/Mailgun.php
+++ b/src/Mailgun/Mailgun.php
@@ -19,8 +19,8 @@ use Mailgun\Lists\OptInHandler;
 use Mailgun\Messages\BatchMessage;
 use Mailgun\Messages\Exceptions;
 use Mailgun\Messages\MessageBuilder;
-use Mailgun\Serializer\ModelSerializer;
-use Mailgun\Serializer\ResponseDeserializer;
+use Mailgun\Deserializer\ModelDeserializer;
+use Mailgun\Deserializer\ResponseDeserializer;
 
 /**
  * This class is the base class for the Mailgun SDK.
@@ -47,7 +47,7 @@ class Mailgun
     /**
      * @var ResponseDeserializer
      */
-    private $serializer;
+    private $deserializer;
 
     /**
      * @var RequestFactory
@@ -58,14 +58,14 @@ class Mailgun
      * @param string|null                 $apiKey
      * @param HttpClient|null             $httpClient
      * @param string                      $apiEndpoint
-     * @param ResponseDeserializer|null   $serializer
+     * @param ResponseDeserializer|null   $deserializer
      * @param HttpClientConfigurator|null $clientConfigurator
      */
     public function __construct(
         $apiKey = null,
         HttpClient $httpClient = null, /* Deprecated, will be removed in 3.0 */
         $apiEndpoint = 'api.mailgun.net', /* Deprecated, will be removed in 3.0 */
-        ResponseDeserializer $serializer = null,
+        ResponseDeserializer $deserializer = null,
         HttpClientConfigurator $clientConfigurator = null
     ) {
         $this->apiKey = $apiKey;
@@ -89,7 +89,7 @@ class Mailgun
 
         $this->httpClient = $clientConfigurator->createConfiguredClient();
         $this->requestFactory = MessageFactoryDiscovery::find();
-        $this->serializer = $serializer ?: new ModelSerializer();
+        $this->deserializer = $deserializer ?: new ModelDeserializer();
     }
 
     /**
@@ -258,7 +258,7 @@ class Mailgun
      */
     public function getStatsApi()
     {
-        return new Api\Stats($this->httpClient, $this->requestFactory, $this->serializer);
+        return new Api\Stats($this->httpClient, $this->requestFactory, $this->deserializer);
     }
 
     /**
@@ -266,6 +266,6 @@ class Mailgun
      */
     public function getDomainApi()
     {
-        return new Api\Domain($this->httpClient, $this->requestFactory, $this->serializer);
+        return new Api\Domain($this->httpClient, $this->requestFactory, $this->deserializer);
     }
 }
diff --git a/src/Mailgun/Resource/Api/Domain/CredentialResponse.php b/src/Mailgun/Resource/Api/Domain/CredentialResponse.php
index 1acb46b..9212439 100644
--- a/src/Mailgun/Resource/Api/Domain/CredentialResponse.php
+++ b/src/Mailgun/Resource/Api/Domain/CredentialResponse.php
@@ -11,6 +11,7 @@ namespace Mailgun\Resource\Api\Domain;
 
 use Mailgun\Assert;
 use Mailgun\Resource\ApiResponse;
+use Mailgun\Resource\Api\ErrorResponse;
 
 /**
  * @author Sean Johnson <sean@mailgun.com>
@@ -34,16 +35,17 @@ final class CredentialResponse implements ApiResponse
      */
     public static function create(array $data)
     {
-        $items = [];
+        if (array_key_exists('items', $data) && array_key_exists('total_count', $data)) {
+            $items = [];
 
-        Assert::keyExists($data, 'total_count');
-        Assert::keyExists($data, 'items');
+            foreach ($data['items'] as $item) {
+                $items[] = CredentialResponseItem::create($item);
+            }
 
-        foreach ($data['items'] as $item) {
-            $items[] = CredentialResponseItem::create($item);
+            return new self($data['total_count'], $items);
+        } else {
+            return ErrorResponse::create($data);
         }
-
-        return new self($data['total_count'], $items);
     }
 
     /**
@@ -54,7 +56,7 @@ final class CredentialResponse implements ApiResponse
     {
         Assert::integer($totalCount);
         Assert::isArray($items);
-        Assert::allIsInstanceOf($items, 'Mailgun\Resource\Api\Domain\Credential');
+        Assert::allIsInstanceOf($items, 'Mailgun\Resource\Api\Domain\CredentialResponseItem');
 
         $this->totalCount = $totalCount;
         $this->items = $items;
diff --git a/src/Mailgun/Resource/Api/Domain/DeleteCredentialResponse.php b/src/Mailgun/Resource/Api/Domain/DeleteCredentialResponse.php
index 56fd1a5..70cab26 100644
--- a/src/Mailgun/Resource/Api/Domain/DeleteCredentialResponse.php
+++ b/src/Mailgun/Resource/Api/Domain/DeleteCredentialResponse.php
@@ -14,6 +14,11 @@ final class DeleteCredentialResponse implements ApiResponse
      */
     private $message;
 
+    /**
+     * @var error
+     */
+    private $error;
+
     /**
      * @var string
      */
@@ -22,9 +27,10 @@ final class DeleteCredentialResponse implements ApiResponse
     /**
      * @param string $message
      */
-    private function __construct($message, $spec)
+    private function __construct($message, $error, $spec)
     {
         $this->message = $message;
+        $this->error = $error;
         $this->spec = $spec;
     }
 
@@ -35,7 +41,11 @@ final class DeleteCredentialResponse implements ApiResponse
      */
     public static function create(array $data)
     {
-        return new self($data['message'], $data['spec']);
+        return new self(
+            isset($data['message']) ? $data['message'] : null,
+            isset($data['error']) ? $data['error'] : null,
+            isset($data['spec']) ? $data['spec'] : null
+        );
     }
 
     /**
@@ -46,6 +56,14 @@ final class DeleteCredentialResponse implements ApiResponse
         return $this->message;
     }
 
+    /**
+     * @return string
+     */
+    public function getError()
+    {
+        return $this->error;
+    }
+
     /**
      * @return string
      */
diff --git a/src/Mailgun/Resource/Api/Domain/DeleteResponse.php b/src/Mailgun/Resource/Api/Domain/DeleteResponse.php
index 1833aab..af0b4a4 100644
--- a/src/Mailgun/Resource/Api/Domain/DeleteResponse.php
+++ b/src/Mailgun/Resource/Api/Domain/DeleteResponse.php
@@ -14,12 +14,18 @@ final class DeleteResponse implements ApiResponse
      */
     private $message;
 
+    /**
+     * @var string
+     */
+    private $error;
+
     /**
      * @param string $message
      */
-    private function __construct($message)
+    private function __construct($message, $error)
     {
         $this->message = $message;
+        $this->error = $error;
     }
 
     /**
@@ -29,7 +35,10 @@ final class DeleteResponse implements ApiResponse
      */
     public static function create(array $data)
     {
-        return new self($data['message']);
+        return new self(
+            isset($data['message']) ? $data['message'] : null,
+            isset($data['error']) ? $data['error'] : null
+        );
     }
 
     /**
@@ -39,4 +48,12 @@ final class DeleteResponse implements ApiResponse
     {
         return $this->message;
     }
+
+    /**
+     * @return string
+     */
+    public function getError()
+    {
+        return $this->error;
+    }
 }
diff --git a/src/Mailgun/Resource/Api/Domain/IndexResponse.php b/src/Mailgun/Resource/Api/Domain/IndexResponse.php
index d0ad6e3..3f181bf 100644
--- a/src/Mailgun/Resource/Api/Domain/IndexResponse.php
+++ b/src/Mailgun/Resource/Api/Domain/IndexResponse.php
@@ -54,7 +54,7 @@ final class IndexResponse implements ApiResponse
     {
         Assert::integer($totalCount);
         Assert::isArray($items);
-        Assert::allIsInstanceOf($items, 'Mailgun\Resource\Api\Domain\SimpleDomain');
+        Assert::allIsInstanceOf($items, 'Mailgun\Resource\Api\Domain\Domain');
 
         $this->totalCount = $totalCount;
         $this->items = $items;
diff --git a/src/Mailgun/Resource/Api/ErrorResponse.php b/src/Mailgun/Resource/Api/ErrorResponse.php
new file mode 100644
index 0000000..67a18bd
--- /dev/null
+++ b/src/Mailgun/Resource/Api/ErrorResponse.php
@@ -0,0 +1,62 @@
+<?php
+
+/**
+ * Copyright (C) 2013-2016 Mailgun.
+ *
+ * This software may be modified and distributed under the terms
+ * of the MIT license.  See the LICENSE file for details.
+ */
+namespace Mailgun\Resource\Api;
+
+use Mailgun\Resource\ApiResponse;
+
+final class ErrorResponse implements ApiResponse
+{
+    /**
+     * @var string
+     */
+    private $message;
+
+    /**
+     * @var string
+     */
+    private $error;
+
+    /**
+     * @param string $error
+     */
+    private function __construct($message, $error)
+    {
+        $this->message = $message;
+        $this->error = $error;
+    }
+
+    /**
+     * @param array data
+     *
+     * @return self
+     */
+    public static function create(array $data)
+    {
+        return new self(
+            isset($data['message']) ? $data['message'] : null,
+            isset($data['error']) ? $data['error'] : null
+        );
+    }
+
+    /**
+     * @return string
+     */
+    public function getMessage()
+    {
+        return $this->message;
+    }
+
+    /**
+     * @return string
+     */
+    public function getError()
+    {
+        return $this->error;
+    }
+}
diff --git a/tests/Api/TestCase.php b/tests/Api/TestCase.php
index ec07291..2f380a3 100644
--- a/tests/Api/TestCase.php
+++ b/tests/Api/TestCase.php
@@ -51,7 +51,7 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
             ->setMethods(['createRequest', 'createResponse'])
             ->getMock();
 
-        $serializer = $this->getMockBuilder('Mailgun\Serializer\ResponseDeserializer')
+        $deserializer = $this->getMockBuilder('Mailgun\Deserializer\ResponseDeserializer')
             ->setMethods(['deserialize'])
             ->getMock();
 
@@ -64,7 +64,7 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
                     'httPut', 'putMultipart',
                 ]
             )
-            ->setConstructorArgs([$httpClient, $requestClient, $serializer])
+            ->setConstructorArgs([$httpClient, $requestClient, $deserializer])
             ->getMock();
     }
 
diff --git a/tests/Integration/DomainApiTest.php b/tests/Integration/DomainApiTest.php
index aa0a5a8..0af8d2a 100644
--- a/tests/Integration/DomainApiTest.php
+++ b/tests/Integration/DomainApiTest.php
@@ -10,16 +10,17 @@
 namespace Mailgun\Tests\Integration;
 
 use Mailgun\Api\Domain;
+use Mailgun\Resource\Api\ErrorResponse;
 use Mailgun\Resource\Api\Domain\CreateCredentialResponse;
-use Mailgun\Resource\Api\Domain\CreateResponse;
 use Mailgun\Resource\Api\Domain\DeleteCredentialResponse;
 use Mailgun\Resource\Api\Domain\DeleteResponse;
-use Mailgun\Resource\Api\Domain\UpdateCredentialResponse;
-use Mailgun\Tests\Api\TestCase;
+use Mailgun\Resource\Api\Domain\Domain as DomainObject;
 use Mailgun\Resource\Api\Domain\CredentialResponseItem;
 use Mailgun\Resource\Api\Domain\CredentialResponse;
 use Mailgun\Resource\Api\Domain\ConnectionResponse;
 use Mailgun\Resource\Api\Domain\UpdateConnectionResponse;
+use Mailgun\Resource\Api\Domain\UpdateCredentialResponse;
+use Mailgun\Tests\Api\TestCase;
 
 /**
  * @author Sean Johnson <sean@mailgun.com>
@@ -28,7 +29,7 @@ class DomainApiTest extends TestCase
 {
     protected function getApiClass()
     {
-        return 'Mailgun\Api\Domains';
+        return 'Mailgun\Api\Domain';
     }
 
     /**
@@ -47,7 +48,7 @@ class DomainApiTest extends TestCase
             }
         }
 
-        $this->assertContainsOnlyInstancesOf(Domain::class, $domainList->getDomains());
+        $this->assertContainsOnlyInstancesOf(DomainObject::class, $domainList->getDomains());
         $this->assertTrue($found);
     }
 
@@ -70,7 +71,7 @@ class DomainApiTest extends TestCase
     /**
      * Performs `DELETE /v3/domains/<domain>` on a non-existent domain.
      */
-    public function testRemoveDomain_NoExist()
+    public function testRemoveDomainNoExist()
     {
         $mg = $this->getMailgunClient();
 
@@ -104,7 +105,7 @@ class DomainApiTest extends TestCase
      * Performs `POST /v3/domains` to attempt to create a domain with duplicate
      * values.
      */
-    public function testDomainCreate_DuplicateValues()
+    public function testDomainCreateDuplicateValues()
     {
         $mg = $this->getMailgunClient();
 
@@ -115,7 +116,7 @@ class DomainApiTest extends TestCase
             false                       // wildcard domain?
         );
         $this->assertNotNull($domain);
-        $this->assertInstanceOf(CreateResponse::class, $domain);
+        $this->assertInstanceOf(ErrorResponse::class, $domain);
         $this->assertEquals('This domain name is already taken', $domain->getMessage());
     }
 
@@ -146,7 +147,7 @@ class DomainApiTest extends TestCase
             'Password.01!'
         );
         $this->assertNotNull($ret);
-        $this->assertInstanceOf(CreateResponse::class, $ret);
+        $this->assertInstanceOf(CreateCredentialResponse::class, $ret);
         $this->assertEquals('Created 1 credentials pair(s)', $ret->getMessage());
     }
 
@@ -220,7 +221,7 @@ class DomainApiTest extends TestCase
 
         $ret = $mg->getDomainApi()->credentials('mailgun.org');
         $this->assertNotNull($ret);
-        $this->assertInstanceOf(CredentialResponse::class, $ret);
+        $this->assertInstanceOf(ErrorResponse::class, $ret);
         $this->assertEquals('Domain not found: mailgun.org', $ret->getMessage());
     }