diff --git a/Dockerfile b/Dockerfile
index 2a91ee08..3031b4f9 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM php:5.6-cli-alpine
+FROM php:7.1-cli-alpine
 
 ARG MOUNTPOINT=/var/www
 ARG COMPOSER_BIN_DIR=/usr/local/bin
diff --git a/composer.json b/composer.json
index 1540d5fa..fe216b87 100644
--- a/composer.json
+++ b/composer.json
@@ -27,9 +27,12 @@
   },
   "scripts": {
     "test": [
-      "@php vendor/bin/phpunit",
-      "@php vendor/bin/sfcs src --progress -vvv"
-    ]
+      "@tests-unit",
+      "@phpcs"
+    ],
+    "tests-unit": "vendor/bin/phpunit",
+    "phpcs": "vendor/bin/sfcs src --progress -vvv",
+    "phpcsfix": "vendor/bin/sfcs src --progress -vvv --autofix"
   },
   "scripts-descriptions": {
     "test" : "Run PHPUnit tests suites and Coding standards validator"
diff --git a/docker-compose.yml b/docker-compose.yml
index 9a5001d7..d941fb89 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -2,6 +2,7 @@ version: '3'
 
 services:
   sf-php-sdk-dev:
+    container_name: sfeed.php-sdk-dev
     image: php-sdk-dev
     build:
       context: .
diff --git a/docs/development/development.md b/docs/development/development.md
index 0d81efdc..d7f2c558 100644
--- a/docs/development/development.md
+++ b/docs/development/development.md
@@ -23,6 +23,11 @@ docker-compose build
 docker-compose run sf-php-sdk-dev composer install --dev
 ```
 
+3. Connect to container
+```bash
+docker-compose run sf-php-sdk-dev /bin/sh
+```
+
 ## Code checks
 
 To help you test your code against our requirements, there is a composer test script configured :
diff --git a/docs/manual/resources/order.md b/docs/manual/resources/order.md
index f321f96b..2a47b427 100644
--- a/docs/manual/resources/order.md
+++ b/docs/manual/resources/order.md
@@ -259,3 +259,23 @@ $operation
 
 $orderApi->execute($operation);
 ```
+
+### Upload documents
+
+To upload order documents, you need the following parameters :
+1. [mandatory] `$reference` : Order reference (eg: 'reference1')
+2. [mandatory] `$channelName` : The channel where the order is from (eg: 'amazon')
+3. [mandatory] `$documents` : One or more documents to upload
+
+Example :
+
+```php
+namespace ShoppingFeed\Sdk\Api\Order; 
+
+$operation = new OrderOperation();
+$operation
+    ->uploadDocument('ref1', 'leroymerlin', new Document\Invoice('/tmp/amazon_ref1_invoice.pdf'))
+    ->uploadDocument('ref2', 'leroymerlin', new Document\Invoice('/tmp/amazon_ref2_invoice.pdf'));
+
+$orderApi->execute($operation);
+```
diff --git a/src/Api/Order/Document/AbstractDocument.php b/src/Api/Order/Document/AbstractDocument.php
new file mode 100644
index 00000000..afdd2e25
--- /dev/null
+++ b/src/Api/Order/Document/AbstractDocument.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace ShoppingFeed\Sdk\Api\Order\Document;
+
+abstract class AbstractDocument
+{
+    /**
+     * @var string
+     */
+    private $path;
+
+    /**
+     * @var string
+     */
+    private $type;
+
+    public function __construct(
+        string $path,
+        string $type
+    )
+    {
+        $this->path = $path;
+        $this->type = $type;
+    }
+
+    public function getPath(): string
+    {
+        return $this->path;
+    }
+
+    public function getType(): string
+    {
+        return $this->type;
+    }
+}
diff --git a/src/Api/Order/Document/Invoice.php b/src/Api/Order/Document/Invoice.php
new file mode 100644
index 00000000..37fe5425
--- /dev/null
+++ b/src/Api/Order/Document/Invoice.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace ShoppingFeed\Sdk\Api\Order\Document;
+
+class Invoice extends AbstractDocument
+{
+    public function __construct(string $path)
+    {
+        parent::__construct($path, 'invoice');
+    }
+}
diff --git a/src/Api/Order/OrderOperation.php b/src/Api/Order/OrderOperation.php
index ebf696d5..57b1ad14 100644
--- a/src/Api/Order/OrderOperation.php
+++ b/src/Api/Order/OrderOperation.php
@@ -1,23 +1,26 @@
 <?php
 namespace ShoppingFeed\Sdk\Api\Order;
 
+use RuntimeException;
 use ShoppingFeed\Sdk\Api;
+use ShoppingFeed\Sdk\Api\Order\Document\AbstractDocument;
+use ShoppingFeed\Sdk\Exception;
 use ShoppingFeed\Sdk\Hal;
 use ShoppingFeed\Sdk\Operation;
-use ShoppingFeed\Sdk\Exception;
 
 class OrderOperation extends Operation\AbstractBulkOperation
 {
     /**
      * Operation types
      */
-    const TYPE_ACCEPT        = 'accept';
-    const TYPE_CANCEL        = 'cancel';
-    const TYPE_REFUSE        = 'refuse';
-    const TYPE_SHIP          = 'ship';
-    const TYPE_REFUND        = 'refund';
-    const TYPE_ACKNOWLEDGE   = 'acknowledge';
-    const TYPE_UNACKNOWLEDGE = 'unacknowledge';
+    public const TYPE_ACCEPT           = 'accept';
+    public const TYPE_CANCEL           = 'cancel';
+    public const TYPE_REFUSE           = 'refuse';
+    public const TYPE_SHIP             = 'ship';
+    public const TYPE_REFUND           = 'refund';
+    public const TYPE_ACKNOWLEDGE      = 'acknowledge';
+    public const TYPE_UNACKNOWLEDGE    = 'unacknowledge';
+    public const TYPE_UPLOAD_DOCUMENTS = 'upload-documents';
 
     /**
      * @var array
@@ -30,6 +33,7 @@ class OrderOperation extends Operation\AbstractBulkOperation
         self::TYPE_REFUND,
         self::TYPE_ACKNOWLEDGE,
         self::TYPE_UNACKNOWLEDGE,
+        self::TYPE_UPLOAD_DOCUMENTS,
     ];
 
     /**
@@ -179,6 +183,27 @@ public function unacknowledge($reference, $channelName)
         return $this;
     }
 
+    /**
+     * @param string                    $reference The channel's order reference
+     * @param string                    $channelName The channel's name
+     * @param Document\AbstractDocument $document
+     *
+     * @return OrderOperation
+     *
+     * @throws Exception\InvalidArgumentException
+     */
+    public function uploadDocument($reference, $channelName, Document\AbstractDocument $document): self
+    {
+        $this->addOperation(
+            $reference,
+            $channelName,
+            self::TYPE_UPLOAD_DOCUMENTS,
+            ['document' => $document]
+        );
+
+        return $this;
+    }
+
     /**
      * Execute all declared operations
      *
@@ -192,10 +217,7 @@ public function execute(Hal\HalLink $link)
         $resources = new \ArrayObject();
 
         foreach ($this->allowedOperationTypes as $type) {
-            $this->eachBatch(
-                $this->createRequestGenerator($type, $link, $requests),
-                $type
-            );
+            $this->populateRequests($type, $link, $requests);
         }
 
         $link->batchSend(
@@ -213,24 +235,81 @@ function (Hal\HalResource $batch) use ($resources) {
         );
     }
 
+    private function populateRequests($type, Hal\HalLink $link, \ArrayAccess $requests): void
+    {
+        // Upload documents require dedicated processing because of file upload specificities
+        if (self::TYPE_UPLOAD_DOCUMENTS === $type) {
+            $this->populateRequestsForUploadDocuments($link, $requests);
+            return;
+        }
+
+        $this->eachBatch(
+            function (array $chunk) use ($type, $link, &$requests) {
+                $requests[] = $link->createRequest(
+                    'POST',
+                    ['operation' => $type],
+                    ['order' => $chunk]
+                );
+            },
+            $type
+        );
+    }
+
     /**
-     * Create request generation callback
+     * Create requests for upload documents operation. We batch request by 20
+     * to not send too many files at once.
      *
-     * @param string      $type
      * @param Hal\HalLink $link
      * @param array       $requests
      *
-     * @return \Closure
+     * @return \Psr\Http\Message\RequestInterface
      */
-    private function createRequestGenerator($type, Hal\HalLink $link, \ArrayAccess $requests)
+    private function populateRequestsForUploadDocuments(Hal\HalLink $link, \ArrayAccess $requests)
     {
-        return function (array $chunk) use ($type, $link, &$requests) {
+        $type = self::TYPE_UPLOAD_DOCUMENTS;
+
+        foreach (array_chunk($this->getOperations($type), 20) as $batch) {
+            $body   = [];
+            $orders = [];
+
+            foreach ($batch as $operation) {
+                /** @var AbstractDocument $document */
+                $document = $operation['document'];
+
+                $resource = fopen($document->getPath(), 'rb');
+
+                if (false === $resource) {
+                    throw new RuntimeException(
+                        sprintf('Unable to read "%s"', $document->getPath())
+                    );
+                }
+
+                $body[] = [
+                    'name'     => 'files[]',
+                    'contents' => $resource,
+                ];
+
+                $orders[] = [
+                    'reference'   => $operation['reference'],
+                    'channelName' => $operation['channelName'],
+                    'documents'   => [
+                        ['type' => $document->getType()],
+                    ],
+                ];
+            }
+
+            $body[] = [
+                'name'     => 'body',
+                'contents' => json_encode(['order' => $orders]),
+            ];
+
             $requests[] = $link->createRequest(
                 'POST',
                 ['operation' => $type],
-                ['order' => $chunk]
+                $body,
+                ['Content-Type' => 'multipart/form-data']
             );
-        };
+        }
     }
 
     /**
diff --git a/src/Hal/HalLink.php b/src/Hal/HalLink.php
index 82e3002f..794ab871 100644
--- a/src/Hal/HalLink.php
+++ b/src/Hal/HalLink.php
@@ -119,7 +119,7 @@ public function withAddedHref($path, $variables = [])
     {
         $instance       = clone $this;
         $instance->href = rtrim($instance->getUri($variables), '/') .
-                          '/' . ltrim($path, '/');
+            '/' . ltrim($path, '/');
 
         return $instance;
     }
@@ -262,15 +262,23 @@ public function send($request, array $config = [])
      *
      * @return \Psr\Http\Message\RequestInterface
      */
-    public function createRequest($method, array $variables = [], $body = null)
+    public function createRequest($method, array $variables = [], $body = null, $headers = [])
     {
-        $uri     = $this->getUri($variables);
-        $method  = strtoupper($method);
-        $headers = [];
+        $uri    = $this->getUri($variables);
+        $method = strtoupper($method);
 
-        if ((null !== $body && '' !== $body) && in_array($method, ['POST', 'PUT', 'PATCH', 'DELETE'])) {
-            $headers['Content-Type'] = 'application/json';
-            $body                    = Json::encode($body);
+        $hasBody = null !== $body && '' !== $body;
+
+        if ($hasBody && in_array($method, ['POST', 'PUT', 'PATCH', 'DELETE'])) {
+            if (! isset($headers['Content-Type'])) {
+                $headers['Content-Type'] = 'application/json';
+            }
+
+            switch ($headers['Content-Type']) {
+                case 'application/json':
+                    $body = Json::encode($body);
+                    break;
+            }
         }
 
         return $this->client->createRequest($method, $uri, $headers, $body);
diff --git a/src/Http/Adapter/GuzzleHTTPAdapter.php b/src/Http/Adapter/GuzzleHTTPAdapter.php
index 3c7e789b..21201f1a 100644
--- a/src/Http/Adapter/GuzzleHTTPAdapter.php
+++ b/src/Http/Adapter/GuzzleHTTPAdapter.php
@@ -91,6 +91,11 @@ public function batchSend(array $requests, array $options = [])
      */
     public function createRequest($method, $uri, array $headers = [], $body = null)
     {
+        if (isset($headers['Content-Type']) && 'multipart/form-data' === $headers['Content-Type']) {
+            unset($headers['Content-Type']);
+            $body = new GuzzleHttp\Psr7\MultipartStream($body);
+        }
+
         return new GuzzleHttp\Psr7\Request($method, $uri, $headers, $body);
     }
 
diff --git a/tests/unit/Api/Order/OrderOperationTest.php b/tests/unit/Api/Order/OrderOperationTest.php
index 7534ec80..fa46fac8 100644
--- a/tests/unit/Api/Order/OrderOperationTest.php
+++ b/tests/unit/Api/Order/OrderOperationTest.php
@@ -1,11 +1,10 @@
 <?php
 namespace ShoppingFeed\Sdk\Test\Api\Order;
 
-use GuzzleHttp\Psr7;
 use PHPUnit\Framework\TestCase;
 use Psr\Http\Message\RequestInterface;
-use Psr\Http\Message\UriInterface;
 use ShoppingFeed\Sdk;
+use ShoppingFeed\Sdk\Api;
 
 class OrderOperationTest extends TestCase
 {
@@ -14,17 +13,17 @@ class OrderOperationTest extends TestCase
     /**
      * Generate operations
      *
-     * @param Sdk\Api\Order\OrderOperation $orderOperation
+     * @param Api\Order\OrderOperation $orderOperation
      *
      * @throws \Exception
      */
-    private function generateOperations(Sdk\Api\Order\OrderOperation $orderOperation)
+    private function generateOperations(Api\Order\OrderOperation $orderOperation)
     {
         for ($i = 0; $i < $this->operationCount; $i++) {
             $orderOperation->addOperation(
                 'ref' . $i,
                 'amazon',
-                Sdk\Api\Order\OrderOperation::TYPE_ACCEPT
+                Api\Order\OrderOperation::TYPE_ACCEPT
             );
         }
     }
@@ -34,12 +33,12 @@ private function generateOperations(Sdk\Api\Order\OrderOperation $orderOperation
      */
     public function testAddOperation()
     {
-        $orderOperation = new Sdk\Api\Order\OrderOperation();
+        $orderOperation = new Api\Order\OrderOperation();
         $this->generateOperations($orderOperation);
 
         $this->assertEquals(
             $this->operationCount,
-            $orderOperation->count(Sdk\Api\Order\OrderOperation::TYPE_ACCEPT)
+            $orderOperation->count(Api\Order\OrderOperation::TYPE_ACCEPT)
         );
     }
 
@@ -49,7 +48,7 @@ public function testAddOperation()
     public function testAcceptOperation()
     {
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['addOperation'])
             ->getMock();
 
@@ -59,12 +58,12 @@ public function testAcceptOperation()
             ->with(
                 'ref1',
                 'amazon',
-                Sdk\Api\Order\OrderOperation::TYPE_ACCEPT,
+                Api\Order\OrderOperation::TYPE_ACCEPT,
                 ['reason' => 'noreason']
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperation::class,
+            Api\Order\OrderOperation::class,
             $instance->accept(
                 'ref1',
                 'amazon',
@@ -79,7 +78,7 @@ public function testAcceptOperation()
     public function testCancelOperation()
     {
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['addOperation'])
             ->getMock();
 
@@ -89,12 +88,12 @@ public function testCancelOperation()
             ->with(
                 'ref1',
                 'amazon',
-                Sdk\Api\Order\OrderOperation::TYPE_CANCEL,
+                Api\Order\OrderOperation::TYPE_CANCEL,
                 ['reason' => 'noreason']
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperation::class,
+            Api\Order\OrderOperation::class,
             $instance->cancel(
                 'ref1',
                 'amazon',
@@ -109,7 +108,7 @@ public function testCancelOperation()
     public function testRefuseOperation()
     {
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['addOperation'])
             ->getMock();
 
@@ -119,11 +118,11 @@ public function testRefuseOperation()
             ->with(
                 'ref1',
                 'amazon',
-                Sdk\Api\Order\OrderOperation::TYPE_REFUSE
+                Api\Order\OrderOperation::TYPE_REFUSE
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperation::class,
+            Api\Order\OrderOperation::class,
             $instance->refuse(
                 'ref1',
                 'amazon'
@@ -137,7 +136,7 @@ public function testRefuseOperation()
     public function testShipOperation()
     {
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['addOperation'])
             ->getMock();
 
@@ -147,7 +146,7 @@ public function testShipOperation()
             ->with(
                 'ref1',
                 'amazon',
-                Sdk\Api\Order\OrderOperation::TYPE_SHIP,
+                Api\Order\OrderOperation::TYPE_SHIP,
                 [
                     'carrier'        => 'ups',
                     'trackingNumber' => '123654abc',
@@ -156,7 +155,7 @@ public function testShipOperation()
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperation::class,
+            Api\Order\OrderOperation::class,
             $instance->ship(
                 'ref1',
                 'amazon',
@@ -167,6 +166,31 @@ public function testShipOperation()
         );
     }
 
+    public function testUploadDocumentOperation()
+    {
+        $document = new Api\Order\Document\Invoice('/tmp/ref1_amazon_invoice.pdf');
+
+        $instance = $this
+            ->getMockBuilder(Api\Order\OrderOperation::class)
+            ->setMethods(['addOperation'])
+            ->getMock();
+
+        $instance
+            ->expects($this->once())
+            ->method('addOperation')
+            ->with(
+                'ref1',
+                'amazon',
+                Api\Order\OrderOperation::TYPE_UPLOAD_DOCUMENTS,
+                ['document' => $document]
+            );
+
+        $this->assertInstanceOf(
+            Api\Order\OrderOperation::class,
+            $instance->uploadDocument('ref1', 'amazon', $document)
+        );
+    }
+
     /**
      * @throws \Exception
      */
@@ -181,7 +205,7 @@ public function testAcknowledgeOperation()
         ];
 
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['addOperation'])
             ->getMock();
 
@@ -191,7 +215,7 @@ public function testAcknowledgeOperation()
             ->with(
                 'ref1',
                 'amazon',
-                Sdk\Api\Order\OrderOperation::TYPE_ACKNOWLEDGE,
+                Api\Order\OrderOperation::TYPE_ACKNOWLEDGE,
                 $this->callback(
                     function ($param) {
                         return $param['status'] === 'success'
@@ -203,7 +227,7 @@ function ($param) {
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperation::class,
+            Api\Order\OrderOperation::class,
             $instance->acknowledge(...$data)
         );
     }
@@ -219,7 +243,7 @@ public function testUnacknowledgeOperation()
             'Unacknowledged',
         ];
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['addOperation'])
             ->getMock();
 
@@ -229,11 +253,11 @@ public function testUnacknowledgeOperation()
             ->with(
                 'ref2',
                 'amazon2',
-                Sdk\Api\Order\OrderOperation::TYPE_UNACKNOWLEDGE
+                Api\Order\OrderOperation::TYPE_UNACKNOWLEDGE
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperation::class,
+            Api\Order\OrderOperation::class,
             $instance->unacknowledge(...$data)
         );
     }
@@ -243,7 +267,7 @@ public function testUnacknowledgeOperation()
      */
     public function testAddWrongOperation()
     {
-        $orderOperation = new Sdk\Api\Order\OrderOperation();
+        $orderOperation = new Api\Order\OrderOperation();
 
         $this->expectException(Sdk\Exception\InvalidArgumentException::class);
 
@@ -264,9 +288,9 @@ public function testExecute()
                 $this->createMock(RequestInterface::class)
             );
 
-        /** @var Sdk\Api\Order\OrderOperation|\PHPUnit_Framework_MockObject_MockObject $instance */
+        /** @var Api\Order\OrderOperation|\PHPUnit_Framework_MockObject_MockObject $instance */
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['getPoolSize'])
             ->getMock();
 
@@ -291,7 +315,7 @@ function (Sdk\Hal\HalResource $resource) use (&$resources) {
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperationResult::class,
+            Api\Order\OrderOperationResult::class,
             $instance->execute($link)
         );
     }
@@ -302,7 +326,7 @@ function (Sdk\Hal\HalResource $resource) use (&$resources) {
     public function testRefundOperation()
     {
         $instance = $this
-            ->getMockBuilder(Sdk\Api\Order\OrderOperation::class)
+            ->getMockBuilder(Api\Order\OrderOperation::class)
             ->setMethods(['addOperation'])
             ->getMock();
 
@@ -312,7 +336,7 @@ public function testRefundOperation()
             ->with(
                 'ref1',
                 'amazon',
-                Sdk\Api\Order\OrderOperation::TYPE_REFUND,
+                Api\Order\OrderOperation::TYPE_REFUND,
                 [
                     'refund' => [
                         'shipping' => true,
@@ -325,7 +349,7 @@ public function testRefundOperation()
             );
 
         $this->assertInstanceOf(
-            Sdk\Api\Order\OrderOperation::class,
+            Api\Order\OrderOperation::class,
             $instance->refund(
                 'ref1',
                 'amazon',
diff --git a/tests/unit/Hal/HalClientTest.php b/tests/unit/Hal/HalClientTest.php
index b2e667d4..b5f0757a 100644
--- a/tests/unit/Hal/HalClientTest.php
+++ b/tests/unit/Hal/HalClientTest.php
@@ -1,10 +1,10 @@
 <?php
 namespace ShoppingFeed\Sdk\Test\Hal;
 
+use GuzzleHttp\Psr7;
 use PHPUnit\Framework\TestCase;
 use Psr\Http\Message;
 use ShoppingFeed\Sdk\Hal;
-use ShoppingFeed\Sdk\Hal\HalResource;
 use ShoppingFeed\Sdk\Http;
 
 class HalClientTest extends TestCase
@@ -61,7 +61,7 @@ public function testCreateResource()
         $response
             ->expects($this->once())
             ->method('getBody')
-            ->willReturn('{"foo":"bar", "foo2":"bar2"}');
+            ->willReturn($this->createStream('{"foo":"bar", "foo2":"bar2"}'));
 
         $instance = new Hal\HalClient('http://fake.uri', $httpClient);
         $resource = $instance->createResource($response);
@@ -155,7 +155,7 @@ public function testSendWithEmptyResponseSkipEncoding()
 
         $response = $this->createMock(Message\ResponseInterface::class);
         $response->method('getStatusCode')->willReturn(200);
-        $response->method('getBody')->willReturn('');
+        $response->method('getBody')->willReturn($this->createStream(''));
 
         $client = $this->createMock(Http\Adapter\AdapterInterface::class);
         $client
@@ -175,7 +175,7 @@ public function testItDecodeResponse()
 
         $response = $this->createMock(Message\ResponseInterface::class);
         $response->method('getStatusCode')->willReturn(200);
-        $response->method('getBody')->willReturn('{"status":"ok"}');
+        $response->method('getBody')->willReturn($this->createStream('{"status":"ok"}'));
 
         $client = $this->createMock(Http\Adapter\AdapterInterface::class);
         $client
@@ -196,4 +196,9 @@ public function testGetAdapter()
 
         $this->assertSame($httpClient, $instance->getAdapter());
     }
+
+    private function createStream(string $contents): Message\StreamInterface
+    {
+        return Psr7\Utils::streamFor($contents);
+    }
 }