diff -u b/gist_filter.module b/gist_filter.module
--- b/gist_filter.module
+++ b/gist_filter.module
@@ -15,7 +15,7 @@
 function gist_filter_theme() {
-  return array(
-    'gist_filter_code' => array(
-      'variables' => array('file' => array()),
-    ),
-  );
+  return [
+    'gist_filter_code' => [
+      'variables' => ['file' => []],
+    ],
+  ];
 }
diff -u b/src/GistFilterCacheDecoratorClient.php b/src/GistFilterCacheDecoratorClient.php
--- b/src/GistFilterCacheDecoratorClient.php
+++ b/src/GistFilterCacheDecoratorClient.php
@@ -1,30 +1,26 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\gist_filter\GistFilterCacheDecoratorClient.
- */
-
 namespace Drupal\gist_filter;
 
 use Drupal\Core\Cache\CacheBackendInterface;
 
 /**
- * Implementation of that caches the results of the wrapped GistFilterClientInterface injected.
+ * Implementation of that caches the results of the wrapped
+ * GistFilterClientInterface injected.
  */
 class GistFilterCacheDecoratorClient implements GistFilterClientInterface {
 
   /**
    * Wrapped GistFilterClientInterface implementation.
    *
-   * @var GistFilterClientInterface
+   * @var \Drupal\gist_filter\GistFilterClientInterface
    */
   protected $client;
 
   /**
    * Cache backend.
    *
-   * @var CacheBackendInterface
+   * @var \Drupal\Core\Cache\CacheBackendInterface
    */
   protected $cacheBackend;
 
@@ -38,9 +34,9 @@
   /**
    * Constructor for proxy implementation.
    *
-   * @param GistFilterClientInterface $client
+   * @param \Drupal\gist_filter\GistFilterClientInterface $client
    *   Wrapped client.
-   * @param CacheBackendInterface $cache_backend
+   * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
    *   Cache backend.
    */
   public function __construct(GistFilterClientInterface $client, CacheBackendInterface $cache_backend) {
@@ -49,7 +45,7 @@
   }
 
   /**
-   * @inheritdoc
+   * {@inheritdoc}
    */
   public function getGist($id) {
     // First, try the static cache.
diff -u b/src/GistFilterClientInterface.php b/src/GistFilterClientInterface.php
--- b/src/GistFilterClientInterface.php
+++ b/src/GistFilterClientInterface.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\gist_filter\GistFilterClientInterface.
- */
-
 namespace Drupal\gist_filter;
 
 /**
diff -u b/src/GistFilterGitHubClient.php b/src/GistFilterGitHubClient.php
--- b/src/GistFilterGitHubClient.php
+++ b/src/GistFilterGitHubClient.php
@@ -1,26 +1,22 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\gist_filter\GistFilterGitHubClient.
- */
-
 namespace Drupal\gist_filter;
 
-use GuzzleHttp\ClientInterface;
+use Drupal\Core\Http\ClientFactory;
 use GuzzleHttp\Exception\RequestException;
 
 /**
- * Implementation of GistFilterClientInterface that requests GitHub api to retrieve a gist.
+ * Implementation of GistFilterClientInterface that requests GitHub api to
+ * retrieve a gist.
  */
 class GistFilterGitHubClient implements GistFilterClientInterface {
 
   /**
-   * The HTTP client to fetch the gist data with.
+   * The HTTP client to fetch the feed data with.
    *
-   * @var \GuzzleHttp\ClientInterface
+   * @var Drupal\Core\Http\ClientFactory
    */
-  private $httpClient;
+  private $httpClientFactory;
 
   /**
    * Constructs a GistFilterGitHubClient instance.
@@ -28,8 +24,8 @@
    * @param \GuzzleHttp\ClientInterface $http_client
    *   The Guzzle HTTP client.
    */
-  public function __construct(ClientInterface $http_client) {
-    $this->httpClient = $http_client;
+  public function __construct(ClientFactory $http_client) {
+    $this->httpClientFactory = $http_client;
   }
 
   /**
@@ -41,7 +37,7 @@
   public function getGist($id) {
     try {
       $url = 'https://api.github.com/gists/' . $id;
-      $response = $this->httpClient->request('GET', $url, array('headers' => array('Accept' => 'application/json')));
+      $response = $this->httpClientFactory->fromOptions()->request('GET', $url, ['headers' => ['Accept' => 'application/json']]);
       $data = (string) $response->getBody();
     }
     catch (RequestException $e) {
diff -u b/src/GitHubRequestException.php b/src/GitHubRequestException.php
--- b/src/GitHubRequestException.php
+++ b/src/GitHubRequestException.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\gist_filter\GitHubRequestException.
- */
-
 namespace Drupal\gist_filter;
 
 /**
diff -u b/src/Plugin/Filter/GistFilter.php b/src/Plugin/Filter/GistFilter.php
--- b/src/Plugin/Filter/GistFilter.php
+++ b/src/Plugin/Filter/GistFilter.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\gist_filter\Plugin\Filter\GistFilter.
- */
-
 namespace Drupal\gist_filter\Plugin\Filter;
 
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
@@ -43,6 +38,8 @@
   protected $renderer;
 
   /**
+   * Client used to retrieve gists.
+   *
    * @var \Drupal\gist_filter\GistFilterGitHubClient
    */
   protected $gitHubClient;
@@ -56,11 +53,11 @@
    * @param array $configuration
    * @param string $plugin_id
    * @param mixed $plugin_definition
-   * @param GistFilterClientInterface $github_client
-   * @param RendererInterface $renderer
-   * @param LoggerInterface $logger
+   * @param \Drupal\gist_filter\GistFilterClientInterface $github_client
+   * @param \Drupal\Core\Render\RendererInterface $renderer
+   * @param \Psr\Log\LoggerInterface $logger
    */
-  public function __construct(array $configuration, $plugin_id, $plugin_definition, GistFilterClientInterface $github_client, RendererInterface $renderer, LoggerInterface $logger) {
+  public function __construct (array $configuration, $plugin_id, $plugin_definition, GistFilterClientInterface $github_client, RendererInterface $renderer, LoggerInterface $logger) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
     $this->gitHubClient = $github_client;
     $this->renderer = $renderer;
@@ -86,9 +83,9 @@
    */
   public function process($text, $language) {
 
-    $text = preg_replace_callback('@\[gist\:(?<id>[\w/]+)(?:\:(?<file>[\w\.]+))?\]@', array($this, gistDisplayEmbed), $text);
-    $text = preg_replace_callback('@\[gistcode\:(?<id>[\w/]+)(?:\:(?<file>[\w\.]+))?\]@', array($this, gistDisplayCode), $text);
-    $text = preg_replace_callback('@\[gistlink\:(?<id>[\w/]+)(?:\:(?<file>[\w\.]+))?\]@', array($this, gistDisplayLink), $text);
+    $text = preg_replace_callback('@\[gist\:(?<id>[\w/]+)(?:\:(?<file>[\w\.]+))?\]@', [$this, 'gistDisplayEmbed'], $text);
+    $text = preg_replace_callback('@\[gistcode\:(?<id>[\w/]+)(?:\:(?<file>[\w\.]+))?\]@', [$this, 'gistDisplayCode'], $text);
+    $text = preg_replace_callback('@\[gistlink\:(?<id>[\w/]+)(?:\:(?<file>[\w\.]+))?\]@', [$this, 'gistDisplayLink'], $text);
 
     return new FilterProcessResult($text);
   }
@@ -96,16 +93,15 @@
   /**
    * {@inheritdoc}
    */
-  public function tips($long = true) {
+  public function tips($long = TRUE) {
 
-    $output = $this->t('Use <code>[gist:#####]</code> for using the default embed method.', '<br />';
-    $output = $this->t('You can use <code>[gist:#####]</code> for displaying just the code of your gist, or <code>[gistlink:#####]</code> for displaying the link of your gist.', '<br />';
-    $output.= $this->t('You may also include a specific file within a multi-file gist with <code>[gist:####:my_file]</code>.');
+    $output = $this->t('Use <code>[gist:#####]</code> for using the default embed method.', '<br />');
+    $output .= $this->t('You can use <code>[gist:#####]</code> for displaying just the code of your gist, or <code>[gistlink:#####]</code> for displaying the link of your gist.', '<br />');
+    $output .= $this->t('You may also include a specific file within a multi-file gist with <code>[gist:####:my_file]</code>.');
 
     return $output;
   }
 
-
   /**
    * Replace the text with the content of the Gist, wrapped in <pre> tags.
    */
@@ -117,19 +113,19 @@
       $build = [];
       // If a file was specified, just render that one file.
       if (isset($matches['file']) && !empty($matches['file']) && isset($data['files'][$matches['file']])) {
-        $build[] = array(
+        $build[] = [
           '#theme' => 'gist_filter_code',
           '#file' => $data['files'][$matches['file']],
-        );
+        ];
 
       }
       // Otherwise, render all files.
       else {
         foreach ($data['files'] as $file) {
-          $build[] = array(
+          $build[] = [
             '#theme' => 'gist_filter_code',
             '#file' => $file,
-          );
+          ];
         }
       }
 
@@ -137,7 +133,7 @@
 
     }
     catch (GitHubRequestException $e) {
-      $this->logger->notice('Error retrieving gist %gist: %error', array('%gist' => $matches['id'], '%error' => $e->getMessage()));
+      $this->logger->notice('Error retrieving gist %gist: %error', ['%gist' => $matches['id'], '%error' => $e->getMessage()]);
     }
   }
 
@@ -150,7 +146,10 @@
       ? $gist_url . '.js?file=' . $matches['file']
       : $gist_url . '.js';
 
-    // Also grab the content and display it in code tags (in case the user does not have JS).
+    /*
+    * Also grab the content and display it in code tags (in case the user does
+    * not have JS).
+    */
     $output = '<noscript>' . $this->gistDisplayCode($matches) . '</noscript>';
     $output .= '<script src="' . $gist_url . '"></script>';
 
diff -u b/src/Tests/GistFilterTestCase.php b/src/Tests/GistFilterTestCase.php
--- b/src/Tests/GistFilterTestCase.php
+++ b/src/Tests/GistFilterTestCase.php
@@ -1,15 +1,9 @@
 <?php
 
-/**
- * @file
- * Tests for the Gist Filter module.
- */
-
 namespace Drupal\gist_filter\Tests;
 
 use Drupal\simpletest\WebTestBase;
 
-
 /**
  * Test the gist_filter module.
  *
@@ -36,10 +30,10 @@
     $this->contentType = $this->drupalCreateContentType();
 
     // Create and log in our user.
-    $this->user = $this->drupalCreateUser(array(
+    $this->user = $this->drupalCreateUser([
       'create ' . $this->contentType->id() . ' content',
       'administer filters',
-    ));
+    ]);
     $this->drupalLogin($this->user);
   }
 
@@ -48,16 +42,14 @@
    */
   public function testEmbedStyle() {
     // Turn on our input filter and set the option to embed.
-    $edit = array(
-      'filters[gist_filter][status]' => 1,
-    );
+    $edit = ['filters[gist_filter][status]' => 1];
 
     $this->drupalPostForm('admin/config/content/formats/manage/plain_text', $edit, t('Save configuration'));
 
-    $edit = array(
+    $edit = [
       'title[0][value]' => $this->randomMachineName(),
       'body[0][value]' => 'Hello! [gist:865412]',
-    );
+    ];
 
     $this->drupalPostForm('node/add/' . $this->contentType->id(), $edit, t('Save'));
     $this->assertResponse(200);
@@ -71,16 +63,14 @@
    */
   public function testEmbedStyleWithFile() {
     // Turn on our input filter and set the option to embed.
-    $edit = array(
-      'filters[gist_filter][status]' => 1,
-    );
+    $edit = ['filters[gist_filter][status]' => 1];
 
     $this->drupalPostForm('admin/config/content/formats/manage/plain_text', $edit, t('Save configuration'));
 
-    $edit = array(
+    $edit = [
       'title[0][value]' => $this->randomMachineName(),
       'body[0][value]' => 'Hello! [gist:865412:php_file.php]',
-    );
+    ];
 
     $this->drupalPostForm('node/add/' . $this->contentType->id(), $edit, t('Save'));
     $this->assertResponse(200);
@@ -95,16 +85,14 @@
   public function testLinkStyle() {
 
     // Turn on our input filter and set the option to link.
-    $edit = array(
-      'filters[gist_filter][status]' => 1,
-    );
+    $edit = ['filters[gist_filter][status]' => 1];
 
     $this->drupalPostForm('admin/config/content/formats/manage/plain_text', $edit, t('Save configuration'));
 
-    $edit = array(
+    $edit = [
       'title[0][value]' => $this->randomMachineName(),
       'body[0][value]' => 'Hello! [gistlink:865412]',
-    );
+    ];
 
     $this->drupalPostForm('node/add/' . $this->contentType->id(), $edit, t('Save'));
     $this->assertResponse(200);
@@ -118,16 +106,14 @@
   public function testLinkStyleWithFile() {
 
     // Turn on our input filter.
-    $edit = array(
-      'filters[gist_filter][status]' => 1,
-    );
+    $edit = ['filters[gist_filter][status]' => 1];
 
     $this->drupalPostForm('admin/config/content/formats/manage/plain_text', $edit, t('Save configuration'));
 
-    $edit = array(
+    $edit = [
       'title[0][value]' => $this->randomMachineName(),
       'body[0][value]' => 'Hello! [gistlink:865412:php_file.php]',
-    );
+    ];
 
     $this->drupalPostForm('node/add/' . $this->contentType->id(), $edit, t('Save'));
     $this->assertResponse(200);
@@ -141,16 +127,14 @@
   public function testCodeTagStyle() {
 
     // Turn on our input filter.
-    $edit = array(
-      'filters[gist_filter][status]' => 1,
-    );
+    $edit = ['filters[gist_filter][status]' => 1];
 
     $this->drupalPostForm('admin/config/content/formats/manage/plain_text', $edit, t('Save configuration'));
 
-    $edit = array(
+    $edit = [
       'title[0][value]' => $this->randomMachineName(),
       'body[0][value]' => 'Hello! [gistcode:865412]',
-    );
+    ];
 
     $this->drupalPostForm('node/add/' . $this->contentType->id(), $edit, t('Save'));
     $this->assertResponse(200);
diff -u b/templates/gist-filter-code.html.twig b/templates/gist-filter-code.html.twig
--- b/templates/gist-filter-code.html.twig
+++ b/templates/gist-filter-code.html.twig
@@ -19 +19,2 @@
-</div>
\ No newline at end of file
+</div>
+
diff -u b/tests/src/Unit/GistFilterCacheDecoratorClientTest.php b/tests/src/Unit/GistFilterCacheDecoratorClientTest.php
--- b/tests/src/Unit/GistFilterCacheDecoratorClientTest.php
+++ b/tests/src/Unit/GistFilterCacheDecoratorClientTest.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\Tests\gist_filter\Unit\GistFilterCacheDecoratorClientTest.
- */
-
 namespace Drupal\Tests\gist_filter\Unit;
 
 use Drupal\Tests\UnitTestCase;
diff -u b/tests/src/Unit/GistFilterGithubClientTest.php b/tests/src/Unit/GistFilterGithubClientTest.php
--- b/tests/src/Unit/GistFilterGithubClientTest.php
+++ b/tests/src/Unit/GistFilterGithubClientTest.php
@@ -1,14 +1,10 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\Tests\gist_filter\Unit\GistFilterGitHubClientTest.
- */
-
 namespace Drupal\Tests\gist_filter\Unit;
 
 use Drupal\Tests\UnitTestCase;
 use Drupal\gist_filter\GistFilterGitHubClient;
+use Drupal\Core\Http\ClientFactory;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Client as GuzzleClient;
 use GuzzleHttp\Psr7\Response as GuzzleResponse;
@@ -43,7 +39,15 @@
       ->method('request')
       ->will($this->returnValue($response));
 
-    $client = new GistFilterGitHubClient($httpClient);
+    $httpClientFactory = $this->getMockBuilder('\Drupal\Core\Http\ClientFactory')
+      ->disableOriginalConstructor()
+      ->getMock();
+
+    $httpClientFactory->expects($this->once())
+      ->method('fromOptions')
+      ->will($this->returnValue($httpClient));
+
+    $client = new GistFilterGitHubClient($httpClientFactory););
     $client->getGist('foo');
 
   }
@@ -78,12 +82,12 @@
 
 
   /**
-   * Generates a GuzzleClient with the mocked responses.
+   * Generates a Drupal\Core\Http\ClientFactory with the mocked responses.
    *
    * @param array $responses
    *   Collection of responses returned by the client.
    *
-   * @return GuzzleClient
+   * @return \Drupal\Core\Http\ClientFactory
    */
   protected function getHttpClient(array $responses = []) {
     if (empty($responses)) {
@@ -92,7 +96,7 @@
 
     $this->mock = new MockHandler($responses);
     $handlerStack = HandlerStack::create($this->mock);
-    $guzzle = new GuzzleClient(array('handler' => $handlerStack));
+    $guzzle = new GuzzleClient(['handler' => $handlerStack]);
 
     return $guzzle;
   }
only in patch2:
unchanged:
--- /dev/null
+++ b/gist_filter.services.yml
@@ -0,0 +1,9 @@
+services:
+  gist_filter_github_client:
+    class: Drupal\gist_filter\GistFilterGitHubClient
+    arguments: ['@http_client_factory']
+
+  gist_filter_cached_github_client:
+    class: Drupal\gist_filter\GistFilterCacheDecoratorClient
+    arguments: ['@gist_filter_github_client', '@cache.default']
+