diff --git a/includes/embeds/class-amp-base-embed-handler.php b/includes/embeds/class-amp-base-embed-handler.php
index f46874b1974..a3d9ee7a9e8 100644
--- a/includes/embeds/class-amp-base-embed-handler.php
+++ b/includes/embeds/class-amp-base-embed-handler.php
@@ -11,18 +11,52 @@
  * Class AMP_Base_Embed_Handler
  */
 abstract class AMP_Base_Embed_Handler {
+	/**
+	 * Default width.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_WIDTH = 600;
+
+	/**
+	 * Default height.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_HEIGHT = 480;
 
+	/**
+	 * Default arguments.
+	 *
+	 * @var array
+	 */
 	protected $args = array();
+
+	/**
+	 * Whether or not conversion was completed.
+	 *
+	 * @var boolean
+	 */
 	protected $did_convert_elements = false;
 
-	abstract function register_embed();
-	abstract function unregister_embed();
+	/**
+	 * Register embed.
+	 */
+	abstract public function register_embed();
 
-	function __construct( $args = array() ) {
+	/**
+	 * Unregister embed.
+	 */
+	abstract public function unregister_embed();
+
+	/**
+	 * AMP_Base_Embed_Handler constructor.
+	 *
+	 * @param array $args Height and width for embed.
+	 */
+	public function __construct( $args = array() ) {
 		$this->args = wp_parse_args( $args, array(
-			'width' => $this->DEFAULT_WIDTH,
+			'width'  => $this->DEFAULT_WIDTH,
 			'height' => $this->DEFAULT_HEIGHT,
 		) );
 	}
diff --git a/includes/embeds/class-amp-dailymotion-embed.php b/includes/embeds/class-amp-dailymotion-embed.php
index 7c58905948f..19db158f8db 100644
--- a/includes/embeds/class-amp-dailymotion-embed.php
+++ b/includes/embeds/class-amp-dailymotion-embed.php
@@ -13,31 +13,59 @@
 class AMP_DailyMotion_Embed_Handler extends AMP_Base_Embed_Handler {
 
 	const URL_PATTERN = '#https?:\/\/(www\.)?dailymotion\.com\/video\/.*#i';
-	const RATIO = 0.5625;
+	const RATIO       = 0.5625;
 
+	/**
+	 * Default width.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_WIDTH = 600;
+
+	/**
+	 * Default height.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_HEIGHT = 338;
 
-	function __construct( $args = array() ) {
+	/**
+	 * AMP_DailyMotion_Embed_Handler constructor.
+	 *
+	 * @param array $args Height, width and maximum width for embed.
+	 */
+	public function __construct( $args = array() ) {
 		parent::__construct( $args );
 
 		if ( isset( $this->args['content_max_width'] ) ) {
-			$max_width = $this->args['content_max_width'];
-			$this->args['width'] = $max_width;
+			$max_width            = $this->args['content_max_width'];
+			$this->args['width']  = $max_width;
 			$this->args['height'] = round( $max_width * self::RATIO );
 		}
 	}
 
-	function register_embed() {
+	/**
+	 * Register embed.
+	 */
+	public function register_embed() {
 		wp_embed_register_handler( 'amp-dailymotion', self::URL_PATTERN, array( $this, 'oembed' ), -1 );
 		add_shortcode( 'dailymotion', array( $this, 'shortcode' ) );
 	}
 
+	/**
+	 * Unregister embed.
+	 */
 	public function unregister_embed() {
 		wp_embed_unregister_handler( 'amp-dailymotion', -1 );
 		remove_shortcode( 'dailymotion' );
 	}
 
+	/**
+	 * Gets AMP-compliant markup for the Dailymotion shortcode.
+	 *
+	 * @param array $attr The Dailymotion attributes.
+	 * @return string Dailymotion shortcode markup.
+	 */
 	public function shortcode( $attr ) {
 		$video_id = false;
 
@@ -53,25 +81,53 @@ public function shortcode( $attr ) {
 			return '';
 		}
 
-		return $this->render( array(
-			'video_id' => $video_id,
-		) );
+		return $this->render(
+			array(
+				'video_id' => $video_id,
+			)
+		);
 	}
 
+	/**
+	 * Render oEmbed.
+	 *
+	 * @see \WP_Embed::shortcode()
+	 *
+	 * @param array  $matches URL pattern matches.
+	 * @param array  $attr    Shortcode attribues.
+	 * @param string $url     URL.
+	 * @param string $rawattr Unmodified shortcode attributes.
+	 * @return string Rendered oEmbed.
+	 */
 	public function oembed( $matches, $attr, $url, $rawattr ) {
 		$video_id = $this->get_video_id_from_url( $url );
-		return $this->render( array(
-			'video_id' => $video_id,
-		) );
+		return $this->render(
+			array(
+				'video_id' => $video_id,
+			)
+		);
 	}
 
+	/**
+	 * Render.
+	 *
+	 * @param array $args Args.
+	 * @return string Rendered.
+	 */
 	public function render( $args ) {
-		$args = wp_parse_args( $args, array(
-			'video_id' => false,
-		) );
+		$args = wp_parse_args(
+			$args, array(
+				'video_id' => false,
+			)
+		);
 
 		if ( empty( $args['video_id'] ) ) {
-			return AMP_HTML_Utils::build_tag( 'a', array( 'href' => esc_url( $args['url'] ), 'class' => 'amp-wp-embed-fallback' ), esc_html( $args['url'] ) );
+			return AMP_HTML_Utils::build_tag(
+				'a', array(
+					'href'  => esc_url( $args['url'] ),
+					'class' => 'amp-wp-embed-fallback',
+				), esc_html( $args['url'] )
+			);
 		}
 
 		$this->did_convert_elements = true;
@@ -80,18 +136,24 @@ public function render( $args ) {
 			'amp-dailymotion',
 			array(
 				'data-videoid' => $args['video_id'],
-				'layout' => 'responsive',
-				'width' => $this->args['width'],
-				'height' => $this->args['height'],
+				'layout'       => 'responsive',
+				'width'        => $this->args['width'],
+				'height'       => $this->args['height'],
 			)
 		);
 	}
 
+	/**
+	 * Determine the video ID from the URL.
+	 *
+	 * @param string $url URL.
+	 * @return integer Video ID.
+	 */
 	private function get_video_id_from_url( $url ) {
 		$parsed_url = AMP_WP_Utils::parse_url( $url );
 		parse_str( $parsed_url['path'], $path );
-		$tok = explode( '/', $parsed_url['path'] );
-		$tok = explode( '_', $tok[2] );
+		$tok      = explode( '/', $parsed_url['path'] );
+		$tok      = explode( '_', $tok[2] );
 		$video_id = $tok[0];
 
 		return $video_id;
diff --git a/includes/embeds/class-amp-twitter-embed.php b/includes/embeds/class-amp-twitter-embed.php
index 8642b5e55d4..735384a16fe 100644
--- a/includes/embeds/class-amp-twitter-embed.php
+++ b/includes/embeds/class-amp-twitter-embed.php
@@ -13,17 +13,29 @@
 class AMP_Twitter_Embed_Handler extends AMP_Base_Embed_Handler {
 	const URL_PATTERN = '#http(s|):\/\/twitter\.com(\/\#\!\/|\/)([a-zA-Z0-9_]{1,20})\/status(es)*\/(\d+)#i';
 
+	/**
+	 * Register embed.
+	 */
 	public function register_embed() {
 		add_shortcode( 'tweet', array( $this, 'shortcode' ) );
 		wp_embed_register_handler( 'amp-twitter', self::URL_PATTERN, array( $this, 'oembed' ), -1 );
 	}
 
+	/**
+	 * Unregister embed.
+	 */
 	public function unregister_embed() {
 		remove_shortcode( 'tweet' );
 		wp_embed_unregister_handler( 'amp-twitter', -1 );
 	}
 
-	function shortcode( $attr ) {
+	/**
+	 * Gets AMP-compliant markup for the Twitter shortcode.
+	 *
+	 * @param array $attr The Twitter attributes.
+	 * @return string Twitter shortcode markup.
+	 */
+	public function shortcode( $attr ) {
 		$attr = wp_parse_args( $attr, array(
 			'tweet' => false,
 		) );
@@ -52,14 +64,25 @@ function shortcode( $attr ) {
 			'amp-twitter',
 			array(
 				'data-tweetid' => $id,
-				'layout' => 'responsive',
-				'width' => $this->args['width'],
-				'height' => $this->args['height'],
+				'layout'       => 'responsive',
+				'width'        => $this->args['width'],
+				'height'       => $this->args['height'],
 			)
 		);
 	}
 
-	function oembed( $matches, $attr, $url, $rawattr ) {
+	/**
+	 * Render oEmbed.
+	 *
+	 * @see \WP_Embed::shortcode()
+	 *
+	 * @param array  $matches URL pattern matches.
+	 * @param array  $attr    Shortcode attribues.
+	 * @param string $url     URL.
+	 * @param string $rawattr Unmodified shortcode attributes.
+	 * @return string Rendered oEmbed.
+	 */
+	public function oembed( $matches, $attr, $url, $rawattr ) {
 		$id = false;
 
 		if ( isset( $matches[5] ) && is_numeric( $matches[5] ) ) {
diff --git a/includes/embeds/class-amp-vimeo-embed.php b/includes/embeds/class-amp-vimeo-embed.php
index 6b334ce6441..f475b894e48 100644
--- a/includes/embeds/class-amp-vimeo-embed.php
+++ b/includes/embeds/class-amp-vimeo-embed.php
@@ -16,39 +16,67 @@ class AMP_Vimeo_Embed_Handler extends AMP_Base_Embed_Handler {
 
 	const RATIO = 0.5625;
 
+	/**
+	 * Default width.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_WIDTH = 600;
+
+	/**
+	 * Default height.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_HEIGHT = 338;
 
-	function __construct( $args = array() ) {
+	/**
+	 * AMP_Vimeo_Embed_Handler constructor.
+	 *
+	 * @param array $args Height, width and maximum width for embed.
+	 */
+	public function __construct( $args = array() ) {
 		parent::__construct( $args );
 
 		if ( isset( $this->args['content_max_width'] ) ) {
-			$max_width = $this->args['content_max_width'];
-			$this->args['width'] = $max_width;
+			$max_width            = $this->args['content_max_width'];
+			$this->args['width']  = $max_width;
 			$this->args['height'] = round( $max_width * self::RATIO );
 		}
 	}
 
-	function register_embed() {
+	/**
+	 * Register embed.
+	 */
+	public function register_embed() {
 		wp_embed_register_handler( 'amp-vimeo', self::URL_PATTERN, array( $this, 'oembed' ), -1 );
 		add_shortcode( 'vimeo', array( $this, 'shortcode' ) );
 		add_filter( 'wp_video_shortcode_override', array( $this, 'video_override' ), 10, 2 );
 	}
 
+	/**
+	 * Unregister embed.
+	 */
 	public function unregister_embed() {
 		wp_embed_unregister_handler( 'amp-vimeo', -1 );
 		remove_shortcode( 'vimeo' );
 	}
 
+	/**
+	 * Gets AMP-compliant markup for the Vimeo shortcode.
+	 *
+	 * @param array $attr The Vimeo attributes.
+	 * @return string Vimeo shortcode markup.
+	 */
 	public function shortcode( $attr ) {
 		$video_id = false;
 
 		if ( isset( $attr['id'] ) ) {
 			$video_id = $attr['id'];
 		} elseif ( isset( $attr['url'] ) ) {
-			$video_id = $this->get_video_id_from_url($attr['url']);
-		}elseif ( isset( $attr[0] ) ) {
-			$video_id = $this->get_video_id_from_url($attr[0]);
+			$video_id = $this->get_video_id_from_url( $attr['url'] );
+		} elseif ( isset( $attr[0] ) ) {
+			$video_id = $this->get_video_id_from_url( $attr[0] );
 		} elseif ( function_exists( 'shortcode_new_to_old_params' ) ) {
 			$video_id = shortcode_new_to_old_params( $attr );
 		}
@@ -57,27 +85,55 @@ public function shortcode( $attr ) {
 			return '';
 		}
 
-		return $this->render( array(
-			'video_id' => $video_id,
-		) );
+		return $this->render(
+			array(
+				'video_id' => $video_id,
+			)
+		);
 	}
 
+	/**
+	 * Render oEmbed.
+	 *
+	 * @see \WP_Embed::shortcode()
+	 *
+	 * @param array  $matches URL pattern matches.
+	 * @param array  $attr    Shortcode attribues.
+	 * @param string $url     URL.
+	 * @param string $rawattr Unmodified shortcode attributes.
+	 * @return string Rendered oEmbed.
+	 */
 	public function oembed( $matches, $attr, $url, $rawattr ) {
 		$video_id = $this->get_video_id_from_url( $url );
 
-		return $this->render( array(
-			'url' => $url,
-			'video_id' => $video_id,
-		) );
+		return $this->render(
+			array(
+				'url'      => $url,
+				'video_id' => $video_id,
+			)
+		);
 	}
 
+	/**
+	 * Render.
+	 *
+	 * @param array $args Args.
+	 * @return string Rendered.
+	 */
 	public function render( $args ) {
-		$args = wp_parse_args( $args, array(
-			'video_id' => false,
-		) );
+		$args = wp_parse_args(
+			$args, array(
+				'video_id' => false,
+			)
+		);
 
 		if ( empty( $args['video_id'] ) ) {
-			return AMP_HTML_Utils::build_tag( 'a', array( 'href' => esc_url( $args['url'] ), 'class' => 'amp-wp-embed-fallback' ), esc_html( $args['url'] ) );
+			return AMP_HTML_Utils::build_tag(
+				'a', array(
+					'href'  => esc_url( $args['url'] ),
+					'class' => 'amp-wp-embed-fallback',
+				), esc_html( $args['url'] )
+			);
 		}
 
 		$this->did_convert_elements = true;
@@ -86,24 +142,27 @@ public function render( $args ) {
 			'amp-vimeo',
 			array(
 				'data-videoid' => $args['video_id'],
-				'layout' => 'responsive',
-				'width' => $this->args['width'],
-				'height' => $this->args['height'],
+				'layout'       => 'responsive',
+				'width'        => $this->args['width'],
+				'height'       => $this->args['height'],
 			)
 		);
 	}
 
-	// get_video_id_from_url()
-	// Takes the last component of a Vimeo URL
-	// and returns it as the associated video id
+	/**
+	 * Determine the video ID from the URL.
+	 *
+	 * @param string $url URL.
+	 * @return integer Video ID.
+	 */
 	private function get_video_id_from_url( $url ) {
 		$parsed_url = parse_url( $url );
 		parse_str( $parsed_url['path'], $path );
 
-		$video_id = "";
+		$video_id = '';
 		if ( $path ) {
-			$tok = explode( '/', $parsed_url['path'] );
-			$video_id = end($tok);
+			$tok      = explode( '/', $parsed_url['path'] );
+			$video_id = end( $tok );
 		}
 
 		return $video_id;
diff --git a/includes/embeds/class-amp-youtube-embed.php b/includes/embeds/class-amp-youtube-embed.php
index a019a6a6334..d8d5bc2d6c2 100644
--- a/includes/embeds/class-amp-youtube-embed.php
+++ b/includes/embeds/class-amp-youtube-embed.php
@@ -14,37 +14,65 @@ class AMP_YouTube_Embed_Handler extends AMP_Base_Embed_Handler {
 	const SHORT_URL_HOST = 'youtu.be';
 	// Only handling single videos. Playlists are handled elsewhere.
 	const URL_PATTERN = '#https?://(?:www\.)?(?:youtube.com/(?:v/|e/|embed/|watch[/\#?])|youtu\.be/).*#i';
-	const RATIO = 0.5625;
+	const RATIO       = 0.5625;
 
+	/**
+	 * Default width.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_WIDTH = 600;
+
+	/**
+	 * Default height.
+	 *
+	 * @var int
+	 */
 	protected $DEFAULT_HEIGHT = 338;
 
-	function __construct( $args = array() ) {
+	/**
+	 * AMP_YouTube_Embed_Handler constructor.
+	 *
+	 * @param array $args Height, width and maximum width for embed.
+	 */
+	public function __construct( $args = array() ) {
 		parent::__construct( $args );
 
 		if ( isset( $this->args['content_max_width'] ) ) {
-			$max_width = $this->args['content_max_width'];
+			$max_width            = $this->args['content_max_width'];
 			$this->args['width']  = $max_width;
 			$this->args['height'] = round( $max_width * self::RATIO );
 		}
 	}
 
-	function register_embed() {
+	/**
+	 * Register embed.
+	 */
+	public function register_embed() {
 		wp_embed_register_handler( 'amp-youtube', self::URL_PATTERN, array( $this, 'oembed' ), -1 );
 		add_shortcode( 'youtube', array( $this, 'shortcode' ) );
 		add_filter( 'wp_video_shortcode_override', array( $this, 'video_override' ), 10, 2 );
 	}
 
+	/**
+	 * Unregister embed.
+	 */
 	public function unregister_embed() {
 		wp_embed_unregister_handler( 'amp-youtube', -1 );
 		remove_shortcode( 'youtube' );
 	}
 
+	/**
+	 * Gets AMP-compliant markup for the YouTube shortcode.
+	 *
+	 * @param array $attr The YouTube attributes.
+	 * @return string YouTube shortcode markup.
+	 */
 	public function shortcode( $attr ) {
-		$url = false;
+		$url      = false;
 		$video_id = false;
 		if ( isset( $attr[0] ) ) {
-			$url = ltrim( $attr[0] , '=' );
+			$url = ltrim( $attr[0], '=' );
 		} elseif ( function_exists( 'shortcode_new_to_old_params' ) ) {
 			$url = shortcode_new_to_old_params( $attr );
 		}
@@ -55,23 +83,49 @@ public function shortcode( $attr ) {
 
 		$video_id = $this->get_video_id_from_url( $url );
 
-		return $this->render( array(
-			'url' => $url,
-			'video_id' => $video_id,
-		) );
+		return $this->render(
+			array(
+				'url'      => $url,
+				'video_id' => $video_id,
+			)
+		);
 	}
 
+	/**
+	 * Render oEmbed.
+	 *
+	 * @see \WP_Embed::shortcode()
+	 *
+	 * @param array  $matches URL pattern matches.
+	 * @param array  $attr    Shortcode attribues.
+	 * @param string $url     URL.
+	 * @param string $rawattr Unmodified shortcode attributes.
+	 * @return string Rendered oEmbed.
+	 */
 	public function oembed( $matches, $attr, $url, $rawattr ) {
 		return $this->shortcode( array( $url ) );
 	}
 
+	/**
+	 * Render.
+	 *
+	 * @param array $args Args.
+	 * @return string Rendered.
+	 */
 	public function render( $args ) {
-		$args = wp_parse_args( $args, array(
-			'video_id' => false,
-		) );
+		$args = wp_parse_args(
+			$args, array(
+				'video_id' => false,
+			)
+		);
 
 		if ( empty( $args['video_id'] ) ) {
-			return AMP_HTML_Utils::build_tag( 'a', array( 'href' => esc_url( $args['url'] ), 'class' => 'amp-wp-embed-fallback' ), esc_html( $args['url'] ) );
+			return AMP_HTML_Utils::build_tag(
+				'a', array(
+					'href'  => esc_url( $args['url'] ),
+					'class' => 'amp-wp-embed-fallback',
+				), esc_html( $args['url'] )
+			);
 		}
 
 		$this->did_convert_elements = true;
@@ -80,25 +134,31 @@ public function render( $args ) {
 			'amp-youtube',
 			array(
 				'data-videoid' => $args['video_id'],
-				'layout' => 'responsive',
-				'width' => $this->args['width'],
-				'height' => $this->args['height'],
+				'layout'       => 'responsive',
+				'width'        => $this->args['width'],
+				'height'       => $this->args['height'],
 			)
 		);
 	}
 
+	/**
+	 * Determine the video ID from the URL.
+	 *
+	 * @param string $url URL.
+	 * @return integer Video ID.
+	 */
 	private function get_video_id_from_url( $url ) {
-		$video_id = false;
+		$video_id   = false;
 		$parsed_url = AMP_WP_Utils::parse_url( $url );
 
 		if ( self::SHORT_URL_HOST === substr( $parsed_url['host'], -strlen( self::SHORT_URL_HOST ) ) ) {
-			// youtu.be/{id}
+			/* youtu.be/{id} */
 			$parts = explode( '/', $parsed_url['path'] );
 			if ( ! empty( $parts ) ) {
 				$video_id = $parts[1];
 			}
 		} else {
-			// ?v={id} or ?list={id}
+			/* The query looks like ?v={id} or ?list={id} */
 			parse_str( $parsed_url['query'], $query_args );
 
 			if ( isset( $query_args['v'] ) ) {
@@ -107,7 +167,7 @@ private function get_video_id_from_url( $url ) {
 		}
 
 		if ( empty( $video_id ) ) {
-			// /(v|e|embed)/{id}
+			/* The path looks like /(v|e|embed)/{id} */
 			$parts = explode( '/', $parsed_url['path'] );
 
 			if ( in_array( $parts[1], array( 'v', 'e', 'embed' ), true ) ) {
@@ -118,8 +178,14 @@ private function get_video_id_from_url( $url ) {
 		return $video_id;
 	}
 
+	/**
+	 * Sanitize the v= argument in the URL.
+	 *
+	 * @param string $value query parameters.
+	 * @return string First set of query parameters.
+	 */
 	private function sanitize_v_arg( $value ) {
-		// Deal with broken params like `?v=123?rel=0`
+		// Deal with broken params like `?v=123?rel=0`.
 		if ( false !== strpos( $value, '?' ) ) {
 			$value = strtok( $value, '?' );
 		}
diff --git a/includes/utils/class-amp-image-dimension-extractor.php b/includes/utils/class-amp-image-dimension-extractor.php
index e659b4fc860..a67f04099e5 100644
--- a/includes/utils/class-amp-image-dimension-extractor.php
+++ b/includes/utils/class-amp-image-dimension-extractor.php
@@ -198,7 +198,7 @@ private static function fetch_images_via_faster_image( $urls_to_fetch, &$images
 		$urls = array_keys( $urls_to_fetch );
 
 		if ( ! function_exists( 'amp_get_fasterimage_client' ) ) {
-			require_once( AMP__DIR__ . '/includes/lib/fasterimage/amp-fasterimage.php' );
+			require_once AMP__DIR__ . '/includes/lib/fasterimage/amp-fasterimage.php';
 		}
 
 		$user_agent = apply_filters( 'amp_extract_image_dimensions_get_user_agent', self::get_default_user_agent() );
diff --git a/jetpack-helper.php b/jetpack-helper.php
index 20b4680e7ba..f6394197c01 100644
--- a/jetpack-helper.php
+++ b/jetpack-helper.php
@@ -63,7 +63,7 @@ function jetpack_amp_build_stats_pixel_url() {
 		$data = compact( 'v', 'j', 'blog', 'post', 'tz', 'srv' );
 	}
 
-	$data['host'] = isset( $_SERVER['HTTP_HOST'] ) ? rawurlencode( $_SERVER['HTTP_HOST'] ) : ''; // input var ok
+	$data['host'] = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : ''; // input var ok.
 	$data['rand'] = 'RANDOM'; // amp placeholder
 	$data['ref'] = 'DOCUMENT_REFERRER'; // amp placeholder
 	$data = array_map( 'rawurlencode' , $data );
diff --git a/phpcs.xml b/phpcs.xml
index 16c6f31e59f..fb1137e950a 100644
--- a/phpcs.xml
+++ b/phpcs.xml
@@ -28,7 +28,7 @@
 	</rule>
 	<rule ref="WordPress.NamingConventions.ValidVariableName">
 		<properties>
-			<property name="customPropertiesWhitelist" value="childNodes,tagName,textContent,parentNode,nodeType,nodeName,nextSibling,firstChild,nodeValue,DEFAULT_ARGS,documentElement,removeChild,ownerDocument" />
+			<property name="customPropertiesWhitelist" value="childNodes,tagName,textContent,parentNode,nodeType,nodeName,nextSibling,firstChild,nodeValue,DEFAULT_ARGS,documentElement,removeChild,ownerDocument,DEFAULT_WIDTH,DEFAULT_HEIGHT" />
 		</properties>
 	</rule>
 
diff --git a/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php b/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php
index a2115bc7e36..ab9fcee3dd1 100644
--- a/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php
+++ b/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php
@@ -409,7 +409,7 @@ public function test_validate_attr_spec_rules( $data, $expected ) {
 
 		$got = $this->invoke_method( $sanitizer, $data['func_name'], array( $node, $data['attribute_name'], $attr_spec_rule ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $source );
 			var_dump( $data );
 		}
@@ -566,7 +566,7 @@ public function test_is_allowed_attribute( $data, $expected ) {
 
 		$got = $this->invoke_method( $sanitizer, $data['func_name'], array( $data['attribute_name'], $attr_spec_list ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $source );
 			var_dump( $data );
 		}
@@ -662,7 +662,7 @@ public function test_remove_node( $data, $expected ) {
 
 		$got = AMP_DOM_Utils::get_content_from_dom( $dom );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 			printf( 'got = %s' .PHP_EOL, $got );
@@ -803,7 +803,7 @@ public function test_replace_node_with_children( $data, $expected ) {
 		$got = AMP_DOM_Utils::get_content_from_dom( $dom );
 		$got = preg_replace( '/(?<=>)\s+(?=<)/', '', $got );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 			printf( 'got = %s' .PHP_EOL, $got );
@@ -865,7 +865,7 @@ public function test_get_ancestor_with_tag_name( $data, $expected ) {
 
 		$got = $this->invoke_method( $sanitizer, 'get_ancestor_with_tag_name', array( $node, $data['ancestor_tag_name'] ) );
 
-		if ( $ancestor_node != $got ) {
+		if ( $ancestor_node !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 		}
@@ -1071,7 +1071,7 @@ public function test_validate_attr_spec_list_for_node( $data, $expected ) {
 
 		$got = $this->invoke_method( $sanitizer, 'validate_attr_spec_list_for_node', array( $node, $data['attr_spec_list'] ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 		}
@@ -1198,7 +1198,7 @@ public function test_check_attr_spec_rule_value( $data, $expected ) {
 
 		$got = $this->invoke_method( $sanitizer, 'check_attr_spec_rule_value', array( $node, $data['attr_name'], $data['attr_spec_rule'] ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 		}
@@ -1350,7 +1350,7 @@ public function test_check_attr_spec_rule_value_casei( $data, $expected ) {
 
 		$got = $this->invoke_method( $sanitizer, 'check_attr_spec_rule_value_casei', array( $node, $data['attr_name'], $data['attr_spec_rule'] ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 		}
@@ -1444,7 +1444,7 @@ public function test_check_attr_spec_rule_blacklisted_value_regex( $data, $expec
 
 		$got = $this->invoke_method( $sanitizer, 'check_attr_spec_rule_blacklisted_value_regex', array( $node, $data['attr_name'], $data['attr_spec_rule'] ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 		}
@@ -1579,7 +1579,7 @@ public function test_check_attr_spec_rule_allowed_protocol( $data, $expected ) {
 
 		$got = $this->invoke_method( $sanitizer, 'check_attr_spec_rule_allowed_protocol', array( $node, $data['attr_name'], $data['attr_spec_rule'] ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 		}
@@ -1728,7 +1728,7 @@ public function test_check_attr_spec_rule_disallowed_relative( $data, $expected
 
 		$got = $this->invoke_method( $sanitizer, 'check_attr_spec_rule_disallowed_relative', array( $node, $data['attr_name'], $data['attr_spec_rule'] ) );
 
-		if ( $expected != $got ) {
+		if ( $expected !== $got ) {
 			printf( 'using source: %s' . PHP_EOL, $data['source'] );
 			var_dump( $data );
 		}
diff --git a/tests/test-amp-analytics-options.php b/tests/test-amp-analytics-options.php
index 274934ffc45..4b99936833c 100644
--- a/tests/test-amp-analytics-options.php
+++ b/tests/test-amp-analytics-options.php
@@ -82,7 +82,7 @@ private function insert_one_option( $type, $config ) {
 	/**
 	 * Test that nothing is added if no analytics option defined in the DB
 	 */
-	function test_no_options() {
+	public function test_no_options() {
 		$options = $this->get_options();
 		$this->assertEmpty( $options );
 	}
@@ -90,7 +90,7 @@ function test_no_options() {
 	/**
 	 * Test that exactly one analytics component is inserted into the DB
 	 */
-	function test_one_option_inserted() {
+	public function test_one_option_inserted() {
 		$this->insert_one_option(
 			$this->vendor,
 			$this->config_one
@@ -103,7 +103,7 @@ function test_one_option_inserted() {
 	/**
 	 * Test that two analytics components are inserted into the DB
 	 */
-	function test_two_options_inserted() {
+	public function test_two_options_inserted() {
 
 		/* Insert analytics option one */
 		$this->insert_one_option(
@@ -124,7 +124,7 @@ function test_two_options_inserted() {
 	/**
 	 * Test that the analytics JS is added to the page
 	 */
-	function test_analytics_js_added() {
+	public function test_analytics_js_added() {
 
 		/* Insert analytics option */
 		$this->insert_one_option(
@@ -137,7 +137,7 @@ function test_analytics_js_added() {
 		$libxml_previous_state = libxml_use_internal_errors( true );
 
 		// Create a new DOM document
-		$dom = new DOMDocument;
+		$dom = new DOMDocument();
 		// Load the rendered page into it
 		$dom->loadHTML( $amp_rendered );
 
@@ -158,7 +158,7 @@ function test_analytics_js_added() {
 	/**
 	 * Test that exactly one analytics component are added to the page
 	 */
-	function test_one_analytics_component_added() {
+	public function test_one_analytics_component_added() {
 
 		/* Insert analytics option */
 		$this->insert_one_option(
@@ -171,7 +171,7 @@ function test_one_analytics_component_added() {
 
 		$libxml_previous_state = libxml_use_internal_errors( true );
 
-		$dom = new DOMDocument;
+		$dom = new DOMDocument();
 		$dom->loadHTML( $amp_rendered );
 
 		$components = $dom->getElementsByTagName( 'amp-analytics' );
@@ -186,7 +186,7 @@ function test_one_analytics_component_added() {
 	/**
 	 * Test that two analytics components are added to the page
 	 */
-	function test_two_analytics_components_added() {
+	public function test_two_analytics_components_added() {
 
 		$this->insert_one_option(
 			$this->vendor,
@@ -202,7 +202,7 @@ function test_two_analytics_components_added() {
 
 		$libxml_previous_state = libxml_use_internal_errors( true );
 
-		$dom = new DOMDocument;
+		$dom = new DOMDocument();
 		$dom->loadHTML( $amp_rendered );
 		$components = $dom->getElementsByTagName( 'amp-analytics' );
 		// Two amp-analytics components should be in the page
diff --git a/tests/test-amp-image-dimension-extractor.php b/tests/test-amp-image-dimension-extractor.php
index f1010ba618d..6dc14c7a5d7 100644
--- a/tests/test-amp-image-dimension-extractor.php
+++ b/tests/test-amp-image-dimension-extractor.php
@@ -1,4 +1,9 @@
 <?php
+/**
+ * Tests for AMP_Image_Dimension_Extractor.
+ *
+ * @package AMP
+ */
 
 define( 'AMP_IMG_DIMENSION_TEST_VALID_FILE', dirname( __FILE__ ) . '/assets/wordpress-logo.png' );
 define( 'AMP_IMG_DIMENSION_TEST_INVALID_FILE', dirname( __FILE__ ) . '/assets/not-exists.png' );
@@ -7,30 +12,43 @@
 define( 'IMG_350', 'http://i0.wp.com/amptest.files.wordpress.com/2017/03/350x150.png' );
 define( 'IMG_1024', 'http://i0.wp.com/amptest.files.wordpress.com/2017/03/1024x768.png' );
 
-class AMP_Image_Dimension_Extractor__Extract__Test extends
-WP_UnitTestCase {
+/**
+ * Tests for AMP_Image_Dimension_Extractor.
+ *
+ * @covers AMP_Image_Dimension_Extractor
+ */
+class AMP_Image_Dimension_Extractor_Extract_Test extends WP_UnitTestCase {
+	/**
+	 * Set up.
+	 */
 	public function setUp() {
 		parent::setUp();
 
-		// We don't want to actually download the images; just testing the extract method
+		// We don't want to actually download the images; just testing the extract method.
 		add_action( 'amp_extract_image_dimensions_batch_callbacks_registered', array( $this, 'disable_downloads' ) );
 	}
 
+	/**
+	 * Disable downloads.
+	 */
 	public function disable_downloads() {
 		remove_all_filters( 'amp_extract_image_dimensions_batch' );
 	}
 
+	/**
+	 * Test where processed URLs should match originals.
+	 */
 	public function test__should_return_original_urls() {
 		$source_urls = array(
 			'https://example.com',
 			'//example.com/no-protocol',
 			'/absolute-url/no-host',
-			'data:image/gif;base64,R0lGODl...', // can't normalize
+			'data:image/gif;base64,R0lGODl...', // can't normalize.
 		);
-		$expected = array(
-			'https://example.com' => false,
-			'//example.com/no-protocol' => false,
-			'/absolute-url/no-host' => false,
+		$expected    = array(
+			'https://example.com'              => false,
+			'//example.com/no-protocol'        => false,
+			'/absolute-url/no-host'            => false,
 			'data:image/gif;base64,R0lGODl...' => false,
 		);
 
@@ -38,18 +56,21 @@ public function test__should_return_original_urls() {
 
 		$this->assertEquals( $expected, $actual );
 	}
-}
 
-class AMP_Image_Dimension_Extractor__Normalize_URL__Test extends WP_UnitTestCase {
-	function get_data() {
+	/**
+	 * Data strings for testing converter.
+	 *
+	 * @return array
+	 */
+	public function get_data() {
 		$site_url = site_url();
 
 		return array(
-			'empty_url' => array(
+			'empty_url'         => array(
 				'',
 				false,
 			),
-			'data_url' => array(
+			'data_url'          => array(
 				'data:image/gif;base64,R0lGODl...',
 				false,
 			),
@@ -57,19 +78,19 @@ function get_data() {
 				'//example.com/file.jpg',
 				'http://example.com/file.jpg',
 			),
-			'path_only' => array(
+			'path_only'         => array(
 				'/path/to/file.png',
 				$site_url . '/path/to/file.png',
 			),
-			'query_only' => array(
+			'query_only'        => array(
 				'?file=file.png',
 				$site_url . '/?file=file.png',
 			),
-			'path_and_query' => array(
+			'path_and_query'    => array(
 				'/path/file.jpg?query=1',
 				$site_url . '/path/file.jpg?query=1',
 			),
-			'normal_url' => array(
+			'normal_url'        => array(
 				'https://example.com/path/to/file.jpg',
 				'https://example.com/path/to/file.jpg',
 			),
@@ -77,26 +98,32 @@ function get_data() {
 	}
 
 	/**
+	 * Test normalizing a URL
+	 *
+	 * @param string $source_url Source.
+	 * @param string $expected_url Expected result.
+	 *
 	 * @dataProvider get_data
 	 */
-	function test__normalize_url( $source_url, $expected_url ) {
+	public function test__normalize_url( $source_url, $expected_url ) {
 		$result_url = AMP_Image_Dimension_Extractor::normalize_url( $source_url );
 
 		$this->assertEquals( $expected_url, $result_url );
 	}
-}
 
-// TODO: tests for transients, errors, lock
-// TODO: mocked tests
-class AMP_Image_Dimension_Extractor__By_Downloading__Test extends WP_UnitTestCase {
-
-	function test__valid_image_file() {
-		$sources = array(
-		    IMG_350 => false,
+	/**
+	 * Test a valid image file.
+	 *
+	 * TODO: tests for transients, errors, lock
+	 * TODO: mocked tests
+	 */
+	public function test__valid_image_file() {
+		$sources  = array(
+			IMG_350 => false,
 		);
 		$expected = array(
-		    IMG_350 => array(
-		        'width' => 350,
+			IMG_350 => array(
+				'width'  => 350,
 				'height' => 150,
 			),
 		);
@@ -106,13 +133,16 @@ function test__valid_image_file() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__valid_image_file_synchronous() {
-		$sources = array(
+	/**
+	 * Test a valid image file synchronously.
+	 */
+	public function test__valid_image_file_synchronous() {
+		$sources  = array(
 			IMG_350 => false,
 		);
 		$expected = array(
 			IMG_350 => array(
-				'width' => 350,
+				'width'  => 350,
 				'height' => 150,
 			),
 		);
@@ -122,18 +152,21 @@ function test__valid_image_file_synchronous() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__multiple_valid_image_files() {
-		$sources = array(
-			IMG_350 => false,
+	/**
+	 * Test multiple valid image files.
+	 */
+	public function test__multiple_valid_image_files() {
+		$sources  = array(
+			IMG_350  => false,
 			IMG_1024 => false,
 		);
 		$expected = array(
-			IMG_350 => array(
-				'width' => 350,
+			IMG_350  => array(
+				'width'  => 350,
 				'height' => 150,
 			),
 			IMG_1024 => array(
-				'width' => 1024,
+				'width'  => 1024,
 				'height' => 768,
 			),
 		);
@@ -143,18 +176,21 @@ function test__multiple_valid_image_files() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__multiple_valid_image_files_synchronous() {
-		$sources = array(
-			IMG_350 => false,
+	/**
+	 * Test multiple valid image files synchronously.
+	 */
+	public function test__multiple_valid_image_files_synchronous() {
+		$sources  = array(
+			IMG_350  => false,
 			IMG_1024 => false,
 		);
 		$expected = array(
-			IMG_350 => array(
-				'width' => 350,
+			IMG_350  => array(
+				'width'  => 350,
 				'height' => 150,
 			),
 			IMG_1024 => array(
-				'width' => 1024,
+				'width'  => 1024,
 				'height' => 768,
 			),
 		);
@@ -164,8 +200,11 @@ function test__multiple_valid_image_files_synchronous() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__invalid_image_file() {
-		$sources = array(
+	/**
+	 * Test an invalid image file.
+	 */
+	public function test__invalid_image_file() {
+		$sources  = array(
 			AMP_IMG_DIMENSION_TEST_INVALID_FILE => false,
 		);
 		$expected = array(
@@ -177,8 +216,11 @@ function test__invalid_image_file() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__invalid_image_file_synchronous() {
-		$sources = array(
+	/**
+	 * Test an invalid image file synchronously.
+	 */
+	public function test__invalid_image_file_synchronous() {
+		$sources  = array(
 			AMP_IMG_DIMENSION_TEST_INVALID_FILE => false,
 		);
 		$expected = array(
@@ -190,20 +232,23 @@ function test__invalid_image_file_synchronous() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__mix_of_valid_and_invalid_image_file() {
-		$sources = array(
-			IMG_350 => false,
+	/**
+	 * Test a mix of valid and invalid image files.
+	 */
+	public function test__mix_of_valid_and_invalid_image_file() {
+		$sources  = array(
+			IMG_350                             => false,
 			AMP_IMG_DIMENSION_TEST_INVALID_FILE => false,
-			IMG_1024 => false,
+			IMG_1024                            => false,
 		);
 		$expected = array(
-			IMG_350 => array(
-				'width' => 350,
+			IMG_350                             => array(
+				'width'  => 350,
 				'height' => 150,
 			),
 			AMP_IMG_DIMENSION_TEST_INVALID_FILE => false,
-			IMG_1024 => array(
-				'width' => 1024,
+			IMG_1024                            => array(
+				'width'  => 1024,
 				'height' => 768,
 			),
 		);
@@ -213,20 +258,23 @@ function test__mix_of_valid_and_invalid_image_file() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__mix_of_valid_and_invalid_image_file_synchronous() {
-		$sources = array(
-			IMG_350 => false,
+	/**
+	 * Test a mix of valid and invalid image files synchronously.
+	 */
+	public function test__mix_of_valid_and_invalid_image_file_synchronous() {
+		$sources  = array(
+			IMG_350                             => false,
 			AMP_IMG_DIMENSION_TEST_INVALID_FILE => false,
-			IMG_1024 => false,
+			IMG_1024                            => false,
 		);
 		$expected = array(
-			IMG_350 => array(
-				'width' => 350,
+			IMG_350                             => array(
+				'width'  => 350,
 				'height' => 150,
 			),
 			AMP_IMG_DIMENSION_TEST_INVALID_FILE => false,
-			IMG_1024 => array(
-				'width' => 1024,
+			IMG_1024                            => array(
+				'width'  => 1024,
 				'height' => 768,
 			),
 		);
@@ -236,8 +284,13 @@ function test__mix_of_valid_and_invalid_image_file_synchronous() {
 		$this->assertEquals( $expected, $dimensions );
 	}
 
-	function test__amp_wp_user_agent() {
-		$expected = 'amp-wp, v' . AMP__VERSION . ', ';
+	/**
+	 * Test get_default_user_agent()
+	 *
+	 * @covers get_default_user_agent()
+	 */
+	public function test__amp_wp_user_agent() {
+		$expected   = 'amp-wp, v' . AMP__VERSION . ', ';
 		$user_agent = AMP_Image_Dimension_Extractor::get_default_user_agent( '' );
 		$user_agent = substr( $user_agent, 0, strlen( $expected ) );
 
diff --git a/tests/test-amp-wp-utils.php b/tests/test-amp-wp-utils.php
index 43f3b3a572e..5ab5d1277ec 100644
--- a/tests/test-amp-wp-utils.php
+++ b/tests/test-amp-wp-utils.php
@@ -1,25 +1,41 @@
 <?php
+/**
+ * Tests for AMP_WP_Utils_Parse_Url_Test.
+ *
+ * @package AMP
+ * @since 0.7
+ */
 
-class AMP_WP_Utils__Parse_Url__Test extends WP_UnitTestCase {
-	function get_test_data() {
+/**
+ * Tests for AMP_WP_Utils_Parse_Url_Test.
+ *
+ * @covers AMP_WP_Utils_Parse_Url_Test
+ */
+class AMP_WP_Utils_Parse_Url_Test extends WP_UnitTestCase {
+	/**
+	 * Data for testing URL parsing.
+	 *
+	 * @return array
+	 */
+	public function get_test_data() {
 		return array(
-			'valid__no_component' => array(
+			'valid__no_component'               => array(
 				'https://example.com/path',
 				array(
 					'scheme' => 'https',
-					'host' => 'example.com',
-					'path' => '/path',
+					'host'   => 'example.com',
+					'path'   => '/path',
 				),
 				-1,
 			),
 
-			'valid__with_component' => array(
+			'valid__with_component'             => array(
 				'https://example.com/path',
 				'example.com',
 				PHP_URL_HOST,
 			),
 
-			'valid__schemaless__no_component' => array(
+			'valid__schemaless__no_component'   => array(
 				'//example.com/path',
 				array(
 					'host' => 'example.com',
@@ -37,9 +53,15 @@ function get_test_data() {
 	}
 
 	/**
+	 * Test URL parsing.
+	 *
+	 * @param string $url       The URL.
+	 * @param string $expected  Expected value.
+	 * @param string $component Derived value.
+	 *
 	 * @dataProvider get_test_data
 	 */
-	function test__method( $url, $expected, $component ) {
+	public function test__method( $url, $expected, $component ) {
 		$actual = AMP_WP_Utils::parse_url( $url, $component );
 
 		$this->assertEquals( $expected, $actual );