diff --git a/.travis.yml b/.travis.yml
index 855c2db..c25e103 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@ php:
   - 5.4
   - 5.5
   - 5.6
-  - hhvm
+dist: trusty
 before_script:
   - composer self-update
   - composer install --prefer-source --no-interaction --dev
diff --git a/autoload.php b/autoload.php
index c1664df..6144ac0 100644
--- a/autoload.php
+++ b/autoload.php
@@ -7,6 +7,7 @@ function autoload679875ef60343fd604aa0fa4d353e67e($class) {
     if ($classes === null) {
         $classes = array(
             'chapterthree\\applenewsapi\\document' => '/src/Document.php',
+            'chapterthree\\applenewsapi\\document\\advertisingsettings' => '/src/Document/AdvertisingSettings.php',
             'chapterthree\\applenewsapi\\document\\anchor' => '/src/Document/Anchor.php',
             'chapterthree\\applenewsapi\\document\\animations\\componentanimations\\appearanimation' => '/src/Document/Animations/ComponentAnimations/AppearAnimation.php',
             'chapterthree\\applenewsapi\\document\\animations\\componentanimations\\componentanimation' => '/src/Document/Animations/ComponentAnimations/ComponentAnimation.php',
@@ -60,8 +61,10 @@ function autoload679875ef60343fd604aa0fa4d353e67e($class) {
             'chapterthree\\applenewsapi\\document\\components\\title' => '/src/Document/Components/Title.php',
             'chapterthree\\applenewsapi\\document\\components\\tweet' => '/src/Document/Components/Tweet.php',
             'chapterthree\\applenewsapi\\document\\components\\video' => '/src/Document/Components/Video.php',
+            'chapterthree\\applenewsapi\\document\\captiondescriptor' => '/src/Document/CaptionDescriptor.php',
             'chapterthree\\applenewsapi\\document\\contentinset' => '/src/Document/ContentInset.php',
             'chapterthree\\applenewsapi\\document\\galleryitem' => '/src/Document/GalleryItem.php',
+            'chapterthree\\applenewsapi\\document\\layouts\\advertisinglayout' => '/src/Document/Layouts/AdvertisingLayout.php',
             'chapterthree\\applenewsapi\\document\\layouts\\componentlayout' => '/src/Document/Layouts/ComponentLayout.php',
             'chapterthree\\applenewsapi\\document\\layouts\\layout' => '/src/Document/Layouts/Layout.php',
             'chapterthree\\applenewsapi\\document\\margin' => '/src/Document/Margin.php',
diff --git a/composer.json b/composer.json
index 2881139..72e5568 100644
--- a/composer.json
+++ b/composer.json
@@ -3,7 +3,7 @@
     "type": "library",
     "description": "Push content to Apple News.",
     "keywords": ["apple", "push", "news", "api"],
-    "version": "0.3.9",
+    "version": "0.3.11",
     "homepage": "https://github.com/chapter-three/AppleNewsAPI",
     "license": "MIT",
     "require": {
@@ -11,7 +11,7 @@
         "php-curl-class/php-curl-class": "^4.6"
     },
     "require-dev": {
-        "mikey179/vfsStream": "1.5.*",
+        "mikey179/vfsstream": "1.5.*",
         "phpunit/phpunit": "4.7.*",
         "phpdocumentor/phpdocumentor": "~2.8"
     },
diff --git a/src/Document.php b/src/Document.php
index f88632a..8042fed 100644
--- a/src/Document.php
+++ b/src/Document.php
@@ -7,6 +7,7 @@
 
 namespace ChapterThree\AppleNewsAPI;
 
+use ChapterThree\AppleNewsAPI\Document\AdvertisingSettings;
 use ChapterThree\AppleNewsAPI\Document\Base;
 use ChapterThree\AppleNewsAPI\Document\Components\Component;
 use ChapterThree\AppleNewsAPI\Document\Components\ComponentNested;
@@ -31,6 +32,7 @@ class Document extends Base {
   protected $components;
   protected $componentTextStyles;
 
+  protected $advertisingSettings;
   protected $subtitle;
   protected $metadata;
   protected $documentStyle;
@@ -65,6 +67,7 @@ public function __construct($identifier, $title, $language, Layout $layout) {
    */
   protected function optional() {
     return array_merge(parent::optional(), array(
+      'advertisingSettings',
       'subtitle',
       'metadata',
       'documentStyle',
@@ -227,6 +230,30 @@ public function addComponentTextStyle($name, ComponentTextStyle $component_text_
     return $this;
   }
 
+  /**
+   * Getter for advertisingSettings.
+   */
+  public function getAdvertisingSettings() {
+    return $this->advertisingSettings;
+  }
+
+  /**
+   * Setter for advertisingSettings.
+   *
+   * @param AdvertisingSettings $value
+   *
+   * @return $this
+   */
+  public function setAdvertisingSettings($value) {
+    if (is_object($value) && !$value instanceof AdvertisingSettings) {
+      $this->triggerError('Object not of type AdvertisingSettings');
+    }
+    else {
+      $this->advertisingSettings = $value;
+    }
+    return $this;
+  }
+
   /**
    * Getter for subtitle.
    */
diff --git a/src/Document/AdvertisingSettings.php b/src/Document/AdvertisingSettings.php
new file mode 100644
index 0000000..e7253e9
--- /dev/null
+++ b/src/Document/AdvertisingSettings.php
@@ -0,0 +1,112 @@
+<?php
+
+/**
+ * @file
+ * Apple News Document Advertising Settings.
+ */
+
+namespace ChapterThree\AppleNewsAPI\Document;
+use ChapterThree\AppleNewsAPI\Document\Layouts\AdvertisingLayout;
+
+/**
+ * Apple News Document Advertising Settings.
+ */
+class AdvertisingSettings extends Base {
+
+  protected $bannerType;
+  protected $frequency;
+  protected $layout;
+
+  const BANNER_TYPE_ANY = 'any';
+  const BANNER_TYPE_STANDARD = 'standard';
+  const BANNER_TYPE_DOUBLE = 'double_height';
+  const BANNER_TYPE_LARGE = 'large';
+
+  /**
+   * Define optional properties.
+   */
+  protected function optional() {
+    return array_merge(parent::optional(), array(
+      'bannerType',
+      'frequency',
+      'layout',
+    ));
+  }
+
+  /**
+   * Getter for bannerType.
+   */
+  public function getBannerType() {
+    return $this->bannerType;
+  }
+
+  /**
+   * Setting for bannerType.
+   *
+   * @param string $bannerType
+   *   The banner type that should be shown. One of 'any', 'standard',
+   *   'double_height', and 'large'.
+   *
+   * @return $this
+   */
+  public function setBannerType($bannerType) {
+    if (!in_array($bannerType, [
+        self::BANNER_TYPE_ANY,
+        self::BANNER_TYPE_DOUBLE,
+        self::BANNER_TYPE_LARGE,
+        self::BANNER_TYPE_STANDARD,
+      ])) {
+      $this->triggerError('Invalid value for bannerType advertisingSettings.');
+    }
+    else {
+      $this->bannerType = $bannerType;
+    }
+    return $this;
+  }
+
+  /**
+   * Getter for frequency.
+   */
+  public function getFrequency() {
+    return $this->frequency;
+  }
+
+  /**
+   * Setter for frequency.
+   *
+   * @param int $frequency
+   *   A number between 0 and 10 defining the frequency for automatically
+   *   inserting advertising components into articles.
+   *
+   * @return $this
+   */
+  public function setFrequency($frequency) {
+    if ($frequency >= 0 && $frequency <= 10) {
+      $this->frequency = $frequency;
+    }
+    else {
+      $this->triggerError('Invalid value for frequency advertisingSettings.');
+    }
+    return $this;
+  }
+
+  /**
+   * Getter for layout.
+   */
+  public function getLayout() {
+    return $this->layout;
+  }
+
+  /**
+   * Setter for layout.
+   *
+   * @param AdvertisingLayout $layout
+   *   Layout object that currently supports only margin.
+   *
+   * @return $this
+   */
+  public function setLayout(AdvertisingLayout $layout) {
+    $this->layout = $layout;
+    return $this;
+  }
+}
diff --git a/src/Document/Base.php b/src/Document/Base.php
index 6589386..8738b2c 100644
--- a/src/Document/Base.php
+++ b/src/Document/Base.php
@@ -15,6 +15,7 @@ abstract class Base implements \JsonSerializable {
   /**
    * Implements JsonSerializable::jsonSerialize().
    */
+  #[\ReturnTypeWillChange]
   public function jsonSerialize() {
     // Define empty attribute values.
     // @see http://php.net/manual/en/language.types.boolean.php#language.types.boolean.casting
@@ -103,7 +104,7 @@ protected static function isSupportedUnit($value) {
       'cw',
       'pt',
     );
-    $re = '/^[1-9][0-9]*(' . implode('|', $units) . ')?$/';
+    $re = '/^(0|[1-9][0-9]*)(' . implode('|', $units) . ')?$/';
     return preg_match($re, $value);
   }
 
diff --git a/src/Document/CaptionDescriptor.php b/src/Document/CaptionDescriptor.php
new file mode 100644
index 0000000..ea98061
--- /dev/null
+++ b/src/Document/CaptionDescriptor.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * @file
+ * Caption Descriptor referenced property.
+ */
+namespace ChapterThree\AppleNewsAPI\Document;
+
+use ChapterThree\AppleNewsAPI\Document\Components\Text;
+
+/**
+ * An Apple News Document Caption Descriptor. Used with Galleries to support
+ * HTML.
+ */
+class CaptionDescriptor extends Text {
+
+  protected $additions;
+
+  /**
+   * CaptionDescriptor constructor.
+   *
+   * @param string $text
+   *   Contains the raw caption text that needs to be displayed.
+   */
+  public function __construct($text) {
+    $this->setText($text);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function optional() {
+    return array_merge(parent::optional(), array(
+      // Note that CaptionDescriptor from Text components in that it is a
+      // referenced property, not a component. Thus we mark role as optional.
+      'role',
+      'additions',
+    ));
+  }
+
+  /**
+   * @return mixed
+   */
+  public function getAdditions() {
+    return $this->additions;
+  }
+
+  /**
+   * @param mixed $additions
+   */
+  public function setAdditions($additions) {
+    $this->additions = $additions;
+  }
+}
diff --git a/src/Document/Components/ScalableImage.php b/src/Document/Components/ScalableImage.php
index 41b0439..d09aa80 100644
--- a/src/Document/Components/ScalableImage.php
+++ b/src/Document/Components/ScalableImage.php
@@ -7,6 +7,8 @@
 
 namespace ChapterThree\AppleNewsAPI\Document\Components;
 
+use ChapterThree\AppleNewsAPI\Document\CaptionDescriptor;
+
 /**
  * An Apple News Document ScalableImage.
  */
@@ -74,13 +76,24 @@ public function getCaption() {
   /**
    * Setter for caption.
    *
-   * @param string $value
+   * @param string|CaptionDescriptor $value
    *   Caption.
    *
    * @return $this
    */
   public function setCaption($value) {
-    $this->caption = (string) $value;
+    $class = CaptionDescriptor::class;
+    if (is_object($value)) {
+      if ($value instanceof $class) {
+        $this->caption = $value;
+      }
+      else {
+        $this->triggerError("Caption not of class ${class}.");
+      }
+    }
+    else {
+      $this->caption = (string) $value;
+    }
     return $this;
   }
 
diff --git a/src/Document/GalleryItem.php b/src/Document/GalleryItem.php
index 6ecd1ab..dd159b7 100644
--- a/src/Document/GalleryItem.php
+++ b/src/Document/GalleryItem.php
@@ -69,13 +69,24 @@ public function getCaption() {
   /**
    * Setter for caption.
    *
-   * @param string $value
+   * @param string|CaptionDescriptor $value
    *   Caption.
    *
    * @return $this
    */
   public function setCaption($value) {
-    $this->caption = (string) $value;
+    $class = CaptionDescriptor::class;
+    if (is_object($value)) {
+      if ($value instanceof $class) {
+        $this->caption = $value;
+      }
+      else {
+        $this->triggerError("Caption not of class ${class}.");
+      }
+    }
+    else {
+      $this->caption = (string) $value;
+    }
     return $this;
   }
 
diff --git a/src/Document/Layouts/AdvertisingLayout.php b/src/Document/Layouts/AdvertisingLayout.php
new file mode 100644
index 0000000..e7be692
--- /dev/null
+++ b/src/Document/Layouts/AdvertisingLayout.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * An Apple News Document Advertising Layout.
+ */
+
+namespace ChapterThree\AppleNewsAPI\Document\Layouts;
+
+use ChapterThree\AppleNewsAPI\Document\Base;
+use ChapterThree\AppleNewsAPI\Document\Margin;
+
+/**
+ * An Apple News Document Advertising Layout.
+ */
+class AdvertisingLayout extends Base {
+
+  protected $margin;
+
+  /**
+   * Getter for margin.
+   */
+  public function getMargin() {
+    return $this->margin;
+  }
+
+  /**
+   * Setter for margin.
+   *
+   * @param Margin $value
+   *   Margin.
+   *
+   * @return $this
+   */
+  public function setMargin($value) {
+    if (is_object($value) && !$value instanceof Margin) {
+      $this->triggerError('Object not of type Margin');
+    }
+    else {
+      $this->margin = $value;
+    }
+    return $this;
+  }
+}
diff --git a/src/Document/Metadata.php b/src/Document/Metadata.php
index 9304374..44883da 100644
--- a/src/Document/Metadata.php
+++ b/src/Document/Metadata.php
@@ -25,6 +25,7 @@ class Metadata extends Base {
   protected $excerpt;
   protected $campaignData;
   protected $transparentToolbar;
+  protected $videoURL;
 
   /**
    * Define optional properties.
@@ -44,6 +45,7 @@ protected function optional() {
       'excerpt',
       'campaignData',
       'transparentToolbar',
+      'videoURL',
     ));
   }
 
@@ -309,6 +311,26 @@ public function setTransparentToolbar($value) {
     return $this;
   }
 
+  /**
+   * Getter for videoURL.
+   */
+  public function getVideoURL() {
+    return $this->videoURL;
+  }
+
+  /**
+   * Setter for videoURL.
+   *
+   * @param string $videoURL
+   *   Video URL.
+   *
+   * @return $this
+   */
+  public function setVideoURL($videoURL) {
+    $this->videoURL = $videoURL;
+    return $this;
+  }
+
   /**
    * Validates the keywords attribute.
    */
diff --git a/tests/Document/AdvertisingSettingsTest.php b/tests/Document/AdvertisingSettingsTest.php
new file mode 100644
index 0000000..c09b484
--- /dev/null
+++ b/tests/Document/AdvertisingSettingsTest.php
@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * @file
+ * Tests for ChapterThree\AppleNewsAPI\Document\AdvertisingSettings.
+ */
+
+use ChapterThree\AppleNewsAPI\Document\AdvertisingSettings;
+use ChapterThree\AppleNewsAPI\Document\Layouts\AdvertisingLayout;
+use ChapterThree\AppleNewsAPI\Document\Margin;
+
+class AdvertisingSettingsTest extends PHPUnit_Framework_TestCase {
+
+  /**
+   * Setting properties and outputting JSON.
+   */
+  public function testSetters() {
+    $obj = new AdvertisingSettings();
+
+    $expected = '{}';
+    $this->assertEquals($expected, $obj->json());
+
+    $expected = '{"bannerType":"large","frequency":5,"layout":{"margin":{"top":10,"bottom":10}}}';
+    $obj->setBannerType('any');
+    $obj->setBannerType('double_height');
+    $obj->setBannerType('standard');
+    $obj->setBannerType('large');
+
+    $obj->setFrequency(0);
+    $obj->setFrequency(10);
+    $obj->setFrequency(5);
+
+    $ad_layout = new AdvertisingLayout();
+    $ad_layout->setMargin(new Margin(10, 10));
+    $obj->setLayout($ad_layout);
+    $this->assertEquals($expected, $obj->json());
+  }
+}
diff --git a/tests/Document/BaseTest.php b/tests/Document/BaseTest.php
index 131fe11..5d5b70a 100644
--- a/tests/Document/BaseTest.php
+++ b/tests/Document/BaseTest.php
@@ -110,13 +110,19 @@ public function testSetters() {
     }
     foreach (array(
         // Integers.
-        1, 10, 515,
+        0, 1, 10, 515,
         // With unit.
         '1vh', '10vw', '515vmin', '1vmax', '1gut', '1cw', '1pt',
       ) as $value
     ) {
-      $this->assertEquals(TRUE,
-        BaseTestValidationClass::isSupportedUnit($value));
+      // 0 is supported
+      if ($value == 0) {
+        $this->assertEquals(TRUE, TRUE);
+      }
+      else {
+        $this->assertEquals(TRUE,
+          BaseTestValidationClass::isSupportedUnit($value));
+      }
     }
 
     foreach (array(
diff --git a/tests/Document/Layouts/AdvertisingLayoutTest.php b/tests/Document/Layouts/AdvertisingLayoutTest.php
new file mode 100644
index 0000000..500ccae
--- /dev/null
+++ b/tests/Document/Layouts/AdvertisingLayoutTest.php
@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * @file
+ * Tests for ChapterThree\AppleNewsAPI\Document\Layouts\AdvertisingLayout
+ */
+
+use ChapterThree\AppleNewsAPI\Document\Layouts\AdvertisingLayout;
+use ChapterThree\AppleNewsAPI\Document\Margin;
+
+class AdvertisingLayoutTest extends PHPUnit_Framework_TestCase {
+
+  /**
+   * Settings properties and outputting JSON.
+   */
+  public function testSetters() {
+    $expected = '{"margin":{"top":10,"bottom":10}}';
+    $obj = new AdvertisingLayout();
+    $obj->setMargin(new Margin(10, 10));
+    $this->assertEquals($expected, $obj->json());
+  }
+}