From a6fe68bb27efbc50e13b7dab8f683faac1fc0d82 Mon Sep 17 00:00:00 2001
From: Riad Benguella <benguella@gmail.com>
Date: Thu, 22 Jun 2017 18:00:20 +0100
Subject: [PATCH 1/7] Blocks: Automatically generate a wrapper classname for
 blocks

---
 blocks/api/serializer.js                      | 22 ++++++++++++++-----
 blocks/api/test/serializer.js                 |  7 ++++--
 blocks/test/fixtures/core-button-center.html  |  2 +-
 .../core-button-center.serialized.html        |  2 +-
 blocks/test/fixtures/core-code.html           |  2 +-
 .../test/fixtures/core-code.serialized.html   |  2 +-
 blocks/test/fixtures/core-embed.html          |  2 +-
 .../test/fixtures/core-embed.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedanimoto.html   |  2 +-
 .../core-embedanimoto.serialized.html         |  2 +-
 blocks/test/fixtures/core-embedcloudup.html   |  2 +-
 .../core-embedcloudup.serialized.html         |  2 +-
 .../test/fixtures/core-embedcollegehumor.html |  2 +-
 .../core-embedcollegehumor.serialized.html    |  2 +-
 .../test/fixtures/core-embeddailymotion.html  |  2 +-
 .../core-embeddailymotion.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedfacebook.html  |  2 +-
 .../core-embedfacebook.serialized.html        |  2 +-
 blocks/test/fixtures/core-embedflickr.html    |  2 +-
 .../fixtures/core-embedflickr.serialized.html |  2 +-
 .../test/fixtures/core-embedfunnyordie.html   |  2 +-
 .../core-embedfunnyordie.serialized.html      |  2 +-
 blocks/test/fixtures/core-embedhulu.html      |  2 +-
 .../fixtures/core-embedhulu.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedimgur.html     |  2 +-
 .../fixtures/core-embedimgur.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedinstagram.html |  2 +-
 .../core-embedinstagram.serialized.html       |  2 +-
 blocks/test/fixtures/core-embedissuu.html     |  2 +-
 .../fixtures/core-embedissuu.serialized.html  |  2 +-
 .../test/fixtures/core-embedkickstarter.html  |  2 +-
 .../core-embedkickstarter.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedmeetupcom.html |  2 +-
 .../core-embedmeetupcom.serialized.html       |  2 +-
 blocks/test/fixtures/core-embedmixcloud.html  |  2 +-
 .../core-embedmixcloud.serialized.html        |  2 +-
 .../test/fixtures/core-embedphotobucket.html  |  2 +-
 .../core-embedphotobucket.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedpolldaddy.html |  2 +-
 .../core-embedpolldaddy.serialized.html       |  2 +-
 blocks/test/fixtures/core-embedreddit.html    |  2 +-
 .../fixtures/core-embedreddit.serialized.html |  2 +-
 .../test/fixtures/core-embedreverbnation.html |  2 +-
 .../core-embedreverbnation.serialized.html    |  2 +-
 .../test/fixtures/core-embedscreencast.html   |  2 +-
 .../core-embedscreencast.serialized.html      |  2 +-
 blocks/test/fixtures/core-embedscribd.html    |  2 +-
 .../fixtures/core-embedscribd.serialized.html |  2 +-
 .../test/fixtures/core-embedslideshare.html   |  2 +-
 .../core-embedslideshare.serialized.html      |  2 +-
 blocks/test/fixtures/core-embedsmugmug.html   |  2 +-
 .../core-embedsmugmug.serialized.html         |  2 +-
 .../test/fixtures/core-embedsoundcloud.html   |  2 +-
 .../core-embedsoundcloud.serialized.html      |  2 +-
 blocks/test/fixtures/core-embedspeaker.html   |  2 +-
 .../core-embedspeaker.serialized.html         |  2 +-
 blocks/test/fixtures/core-embedspotify.html   |  2 +-
 .../core-embedspotify.serialized.html         |  2 +-
 blocks/test/fixtures/core-embedted.html       |  2 +-
 .../fixtures/core-embedted.serialized.html    |  2 +-
 blocks/test/fixtures/core-embedtumblr.html    |  2 +-
 .../fixtures/core-embedtumblr.serialized.html |  2 +-
 blocks/test/fixtures/core-embedtwitter.html   |  2 +-
 .../core-embedtwitter.serialized.html         |  2 +-
 .../test/fixtures/core-embedvideopress.html   |  2 +-
 .../core-embedvideopress.serialized.html      |  2 +-
 blocks/test/fixtures/core-embedvimeo.html     |  2 +-
 .../fixtures/core-embedvimeo.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedvine.html      |  2 +-
 .../fixtures/core-embedvine.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedwordpress.html |  2 +-
 .../core-embedwordpress.serialized.html       |  2 +-
 .../test/fixtures/core-embedwordpresstv.html  |  2 +-
 .../core-embedwordpresstv.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedyoutube.html   |  2 +-
 .../core-embedyoutube.serialized.html         |  2 +-
 .../fixtures/core-freeform.serialized.html    |  2 +-
 blocks/test/fixtures/core-gallery.html        |  2 +-
 .../fixtures/core-gallery.serialized.html     |  2 +-
 blocks/test/fixtures/core-heading-h2-em.html  |  2 +-
 .../core-heading-h2-em.serialized.html        |  2 +-
 blocks/test/fixtures/core-heading-h2.html     |  2 +-
 .../fixtures/core-heading-h2.serialized.html  |  2 +-
 .../fixtures/core-image-center-caption.html   |  2 +-
 .../core-image-center-caption.serialized.html |  2 +-
 blocks/test/fixtures/core-image.html          |  2 +-
 .../test/fixtures/core-image.serialized.html  |  2 +-
 blocks/test/fixtures/core-list-ul.html        |  2 +-
 .../fixtures/core-list-ul.serialized.html     |  2 +-
 blocks/test/fixtures/core-preformatted.html   |  2 +-
 .../core-preformatted.serialized.html         |  2 +-
 blocks/test/fixtures/core-pullquote.html      |  2 +-
 .../fixtures/core-pullquote.serialized.html   |  2 +-
 blocks/test/fixtures/core-quote-style-1.html  |  2 +-
 .../core-quote-style-1.serialized.html        |  2 +-
 blocks/test/fixtures/core-quote-style-2.html  |  2 +-
 .../core-quote-style-2.serialized.html        |  2 +-
 blocks/test/fixtures/core-separator.html      |  2 +-
 .../fixtures/core-separator.serialized.html   |  2 +-
 blocks/test/fixtures/core-table.html          |  2 +-
 .../test/fixtures/core-table.serialized.html  |  2 +-
 .../test/fixtures/core-text-align-right.html  |  2 +-
 .../core-text-align-right.serialized.html     |  2 +-
 103 files changed, 123 insertions(+), 108 deletions(-)

diff --git a/blocks/api/serializer.js b/blocks/api/serializer.js
index 836afa5fc0db7..4991f5b49288c 100644
--- a/blocks/api/serializer.js
+++ b/blocks/api/serializer.js
@@ -1,13 +1,14 @@
 /**
  * External dependencies
  */
-import { isEmpty, map, reduce } from 'lodash';
+import { isEmpty, map, reduce, kebabCase, isObject } from 'lodash';
 import { html as beautifyHtml } from 'js-beautify';
+import classnames from 'classnames';
 
 /**
  * WordPress dependencies
  */
-import { Component, createElement, renderToString } from 'element';
+import { Component, createElement, renderToString, cloneElement, Children } from 'element';
 
 /**
  * Internal dependencies
@@ -20,10 +21,11 @@ import { parseBlockAttributes } from './parser';
  * static markup to be saved.
  *
  * @param  {Function|WPComponent} save       Save render implementation
+ * @param  {String}               blockName  Block name
  * @param  {Object}               attributes Block attributes
  * @return {string}                          Save content
  */
-export function getSaveContent( save, attributes ) {
+export function getSaveContent( save, blockName, attributes ) {
 	let rawContent;
 
 	if ( save.prototype instanceof Component ) {
@@ -37,8 +39,18 @@ export function getSaveContent( save, attributes ) {
 		}
 	}
 
+	// Adding a generic classname
+	const addClassnameToElement = ( element ) => {
+		if ( ! element || ! isObject( element ) ) {
+			return element;
+		}
+		const className = classnames( element.props.className, `wp-block-${ kebabCase( blockName ) }` );
+		return cloneElement( element, { className } );
+	};
+	const contentWithClassname = Children.map( rawContent, addClassnameToElement );
+
 	// Otherwise, infer as element
-	return renderToString( rawContent );
+	return renderToString( contentWithClassname );
 }
 
 const escapeDoubleQuotes = value => value.replace( /"/g, '\"' );
@@ -107,7 +119,7 @@ function asNameValuePair( value, key ) {
 export function serializeBlock( block ) {
 	const blockName = block.name;
 	const blockType = getBlockType( blockName );
-	const saveContent = getSaveContent( blockType.save, block.attributes );
+	const saveContent = getSaveContent( blockType.save, blockName, block.attributes );
 	const saveAttributes = getCommentAttributes( block.attributes, parseBlockAttributes( saveContent, blockType ) );
 
 	const serializedAttributes = ! isEmpty( saveAttributes )
diff --git a/blocks/api/test/serializer.js b/blocks/api/test/serializer.js
index 810cfd9ccc629..0b244eba3f803 100644
--- a/blocks/api/test/serializer.js
+++ b/blocks/api/test/serializer.js
@@ -26,6 +26,7 @@ describe( 'block serializer', () => {
 			it( 'should return string verbatim', () => {
 				const saved = getSaveContent(
 					( { attributes } ) => attributes.fruit,
+					'core/fruit',
 					{ fruit: 'Bananas' }
 				);
 
@@ -35,10 +36,11 @@ describe( 'block serializer', () => {
 			it( 'should return element as string if save returns element', () => {
 				const saved = getSaveContent(
 					( { attributes } ) => createElement( 'div', null, attributes.fruit ),
+					'core/fruit',
 					{ fruit: 'Bananas' }
 				);
 
-				expect( saved ).to.equal( '<div>Bananas</div>' );
+				expect( saved ).to.equal( '<div class="wp-block-core-fruit">Bananas</div>' );
 			} );
 		} );
 
@@ -50,6 +52,7 @@ describe( 'block serializer', () => {
 							return createElement( 'div', null, this.props.attributes.fruit );
 						}
 					},
+					'core/fruit',
 					{ fruit: 'Bananas' }
 				);
 
@@ -124,7 +127,7 @@ describe( 'block serializer', () => {
 					},
 				},
 			];
-			const expectedPostContent = '<!-- wp:core/test-block align="left" -->\n<p>Ribs & Chicken</p>\n<!-- /wp:core/test-block -->';
+			const expectedPostContent = '<!-- wp:core/test-block align="left" -->\n<p class="wp-block-core-test-block">Ribs & Chicken</p>\n<!-- /wp:core/test-block -->';
 
 			expect( serialize( blockList ) ).to.eql( expectedPostContent );
 		} );
diff --git a/blocks/test/fixtures/core-button-center.html b/blocks/test/fixtures/core-button-center.html
index b80f97864c293..312b3532e72e7 100644
--- a/blocks/test/fixtures/core-button-center.html
+++ b/blocks/test/fixtures/core-button-center.html
@@ -1,3 +1,3 @@
 <!-- wp:core/button align="center" -->
-<div class="aligncenter"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
+<div class="aligncenter wp-block-core-button"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
 <!-- /wp:core/button -->
diff --git a/blocks/test/fixtures/core-button-center.serialized.html b/blocks/test/fixtures/core-button-center.serialized.html
index c360f9e247a91..971bb48cfc038 100644
--- a/blocks/test/fixtures/core-button-center.serialized.html
+++ b/blocks/test/fixtures/core-button-center.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/button align="center" -->
-<div class="aligncenter"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
+<div class="aligncenter wp-block-core-button"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
 <!-- /wp:core/button -->
 
diff --git a/blocks/test/fixtures/core-code.html b/blocks/test/fixtures/core-code.html
index 0c00ab494b2f9..bbfc1b5a80f91 100644
--- a/blocks/test/fixtures/core-code.html
+++ b/blocks/test/fixtures/core-code.html
@@ -1,5 +1,5 @@
 <!-- wp:core/code -->
-<pre><code>export default function MyButton() {
+<pre class="wp-block-core-code"><code>export default function MyButton() {
 	return &lt;Button&gt;Click Me!&lt;/Button&gt;;
 }</code></pre>
 <!-- /wp:core/code -->
diff --git a/blocks/test/fixtures/core-code.serialized.html b/blocks/test/fixtures/core-code.serialized.html
index fbf78a33703c0..f74b38be87235 100644
--- a/blocks/test/fixtures/core-code.serialized.html
+++ b/blocks/test/fixtures/core-code.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/code -->
-<pre><code>export default function MyButton() {
+<pre class="wp-block-core-code"><code>export default function MyButton() {
 	return &lt;Button&gt;Click Me!&lt;/Button&gt;;
 }</code></pre>
 <!-- /wp:core/code -->
diff --git a/blocks/test/fixtures/core-embed.html b/blocks/test/fixtures/core-embed.html
index af8b876de71e0..a22b8055dbb14 100644
--- a/blocks/test/fixtures/core-embed.html
+++ b/blocks/test/fixtures/core-embed.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embed url="https://example.com/" -->
-<figure>
+<figure class="wp-block-core-embed">
     https://example.com/
     <figcaption>Embedded content from an example URL</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embed.serialized.html b/blocks/test/fixtures/core-embed.serialized.html
index b8b1e50e7afef..b79ba1e98afb5 100644
--- a/blocks/test/fixtures/core-embed.serialized.html
+++ b/blocks/test/fixtures/core-embed.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embed url="https://example.com/" -->
-<figure>
+<figure class="wp-block-core-embed">
     https://example.com/
     <figcaption>Embedded content from an example URL</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedanimoto.html b/blocks/test/fixtures/core-embedanimoto.html
index 0e464a377f248..0675dad35eb3b 100644
--- a/blocks/test/fixtures/core-embedanimoto.html
+++ b/blocks/test/fixtures/core-embedanimoto.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedanimoto url="https://animoto.com/" -->
-<figure>
+<figure class="wp-block-core-embedanimoto">
     https://animoto.com/
     <figcaption>Embedded content from animoto</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedanimoto.serialized.html b/blocks/test/fixtures/core-embedanimoto.serialized.html
index e33c67b8256d6..22508b2fc631d 100644
--- a/blocks/test/fixtures/core-embedanimoto.serialized.html
+++ b/blocks/test/fixtures/core-embedanimoto.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedanimoto url="https://animoto.com/" -->
-<figure>
+<figure class="wp-block-core-embedanimoto">
     https://animoto.com/
     <figcaption>Embedded content from animoto</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcloudup.html b/blocks/test/fixtures/core-embedcloudup.html
index 4650c84b4b703..73922f0aecfba 100644
--- a/blocks/test/fixtures/core-embedcloudup.html
+++ b/blocks/test/fixtures/core-embedcloudup.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcloudup url="https://cloudup.com/" -->
-<figure>
+<figure class="wp-block-core-embedcloudup">
     https://cloudup.com/
     <figcaption>Embedded content from cloudup</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcloudup.serialized.html b/blocks/test/fixtures/core-embedcloudup.serialized.html
index 02951c1171ec5..5515f4124b29e 100644
--- a/blocks/test/fixtures/core-embedcloudup.serialized.html
+++ b/blocks/test/fixtures/core-embedcloudup.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcloudup url="https://cloudup.com/" -->
-<figure>
+<figure class="wp-block-core-embedcloudup">
     https://cloudup.com/
     <figcaption>Embedded content from cloudup</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcollegehumor.html b/blocks/test/fixtures/core-embedcollegehumor.html
index 5ecdbc3e4dd88..1667705e6b095 100644
--- a/blocks/test/fixtures/core-embedcollegehumor.html
+++ b/blocks/test/fixtures/core-embedcollegehumor.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcollegehumor url="https://collegehumor.com/" -->
-<figure>
+<figure class="wp-block-core-embedcollegehumor">
     https://collegehumor.com/
     <figcaption>Embedded content from collegehumor</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcollegehumor.serialized.html b/blocks/test/fixtures/core-embedcollegehumor.serialized.html
index 82ffd18b7c829..4834b97cdea6b 100644
--- a/blocks/test/fixtures/core-embedcollegehumor.serialized.html
+++ b/blocks/test/fixtures/core-embedcollegehumor.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcollegehumor url="https://collegehumor.com/" -->
-<figure>
+<figure class="wp-block-core-embedcollegehumor">
     https://collegehumor.com/
     <figcaption>Embedded content from collegehumor</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embeddailymotion.html b/blocks/test/fixtures/core-embeddailymotion.html
index 08bed7270fe70..2eb58a3647a1b 100644
--- a/blocks/test/fixtures/core-embeddailymotion.html
+++ b/blocks/test/fixtures/core-embeddailymotion.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embeddailymotion url="https://dailymotion.com/" -->
-<figure>
+<figure class="wp-block-core-embeddailymotion">
     https://dailymotion.com/
     <figcaption>Embedded content from dailymotion</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embeddailymotion.serialized.html b/blocks/test/fixtures/core-embeddailymotion.serialized.html
index 62f55871d1e1f..de05b3c4e45f3 100644
--- a/blocks/test/fixtures/core-embeddailymotion.serialized.html
+++ b/blocks/test/fixtures/core-embeddailymotion.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embeddailymotion url="https://dailymotion.com/" -->
-<figure>
+<figure class="wp-block-core-embeddailymotion">
     https://dailymotion.com/
     <figcaption>Embedded content from dailymotion</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfacebook.html b/blocks/test/fixtures/core-embedfacebook.html
index 4a5044c13d6cd..36b195fca0219 100644
--- a/blocks/test/fixtures/core-embedfacebook.html
+++ b/blocks/test/fixtures/core-embedfacebook.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfacebook url="https://facebook.com/" -->
-<figure>
+<figure class="wp-block-core-embedfacebook">
     https://facebook.com/
     <figcaption>Embedded content from facebook</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfacebook.serialized.html b/blocks/test/fixtures/core-embedfacebook.serialized.html
index efda5813641da..e4e3b8cd0e2d8 100644
--- a/blocks/test/fixtures/core-embedfacebook.serialized.html
+++ b/blocks/test/fixtures/core-embedfacebook.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfacebook url="https://facebook.com/" -->
-<figure>
+<figure class="wp-block-core-embedfacebook">
     https://facebook.com/
     <figcaption>Embedded content from facebook</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedflickr.html b/blocks/test/fixtures/core-embedflickr.html
index 2325790efcab2..54eba6e3b4d9f 100644
--- a/blocks/test/fixtures/core-embedflickr.html
+++ b/blocks/test/fixtures/core-embedflickr.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedflickr url="https://flickr.com/" -->
-<figure>
+<figure class="wp-block-core-embedflickr">
     https://flickr.com/
     <figcaption>Embedded content from flickr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedflickr.serialized.html b/blocks/test/fixtures/core-embedflickr.serialized.html
index 4d86c30f5b881..7fab45c0d0032 100644
--- a/blocks/test/fixtures/core-embedflickr.serialized.html
+++ b/blocks/test/fixtures/core-embedflickr.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedflickr url="https://flickr.com/" -->
-<figure>
+<figure class="wp-block-core-embedflickr">
     https://flickr.com/
     <figcaption>Embedded content from flickr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfunnyordie.html b/blocks/test/fixtures/core-embedfunnyordie.html
index 67e845a743e95..09c99b96ce3ab 100644
--- a/blocks/test/fixtures/core-embedfunnyordie.html
+++ b/blocks/test/fixtures/core-embedfunnyordie.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfunnyordie url="https://funnyordie.com/" -->
-<figure>
+<figure class="wp-block-core-embedfunnyordie">
     https://funnyordie.com/
     <figcaption>Embedded content from funnyordie</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfunnyordie.serialized.html b/blocks/test/fixtures/core-embedfunnyordie.serialized.html
index bba227b1c1956..a8a9aa567f8aa 100644
--- a/blocks/test/fixtures/core-embedfunnyordie.serialized.html
+++ b/blocks/test/fixtures/core-embedfunnyordie.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfunnyordie url="https://funnyordie.com/" -->
-<figure>
+<figure class="wp-block-core-embedfunnyordie">
     https://funnyordie.com/
     <figcaption>Embedded content from funnyordie</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedhulu.html b/blocks/test/fixtures/core-embedhulu.html
index 749b3ecb99aee..fb19c1c5d5151 100644
--- a/blocks/test/fixtures/core-embedhulu.html
+++ b/blocks/test/fixtures/core-embedhulu.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedhulu url="https://hulu.com/" -->
-<figure>
+<figure class="wp-block-core-embedhulu">
     https://hulu.com/
     <figcaption>Embedded content from hulu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedhulu.serialized.html b/blocks/test/fixtures/core-embedhulu.serialized.html
index c9c5b31537a69..51211ebfde4a2 100644
--- a/blocks/test/fixtures/core-embedhulu.serialized.html
+++ b/blocks/test/fixtures/core-embedhulu.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedhulu url="https://hulu.com/" -->
-<figure>
+<figure class="wp-block-core-embedhulu">
     https://hulu.com/
     <figcaption>Embedded content from hulu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedimgur.html b/blocks/test/fixtures/core-embedimgur.html
index 93f03e68d48d8..cf9ce949285e7 100644
--- a/blocks/test/fixtures/core-embedimgur.html
+++ b/blocks/test/fixtures/core-embedimgur.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedimgur url="https://imgur.com/" -->
-<figure>
+<figure class="wp-block-core-embedimgur">
     https://imgur.com/
     <figcaption>Embedded content from imgur</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedimgur.serialized.html b/blocks/test/fixtures/core-embedimgur.serialized.html
index e1e3510c97eab..a22ec4622e057 100644
--- a/blocks/test/fixtures/core-embedimgur.serialized.html
+++ b/blocks/test/fixtures/core-embedimgur.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedimgur url="https://imgur.com/" -->
-<figure>
+<figure class="wp-block-core-embedimgur">
     https://imgur.com/
     <figcaption>Embedded content from imgur</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedinstagram.html b/blocks/test/fixtures/core-embedinstagram.html
index 12dc0d1ec0853..b74d60f360a33 100644
--- a/blocks/test/fixtures/core-embedinstagram.html
+++ b/blocks/test/fixtures/core-embedinstagram.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedinstagram url="https://instagram.com/" -->
-<figure>
+<figure class="wp-block-core-embedinstagram">
     https://instagram.com/
     <figcaption>Embedded content from instagram</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedinstagram.serialized.html b/blocks/test/fixtures/core-embedinstagram.serialized.html
index 018a38ab8d52b..789314d81df37 100644
--- a/blocks/test/fixtures/core-embedinstagram.serialized.html
+++ b/blocks/test/fixtures/core-embedinstagram.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedinstagram url="https://instagram.com/" -->
-<figure>
+<figure class="wp-block-core-embedinstagram">
     https://instagram.com/
     <figcaption>Embedded content from instagram</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedissuu.html b/blocks/test/fixtures/core-embedissuu.html
index 6849278719bc4..537bed06aef59 100644
--- a/blocks/test/fixtures/core-embedissuu.html
+++ b/blocks/test/fixtures/core-embedissuu.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedissuu url="https://issuu.com/" -->
-<figure>
+<figure class="wp-block-core-embedissuu">
     https://issuu.com/
     <figcaption>Embedded content from issuu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedissuu.serialized.html b/blocks/test/fixtures/core-embedissuu.serialized.html
index 18903978bd6e1..09fa6af235cff 100644
--- a/blocks/test/fixtures/core-embedissuu.serialized.html
+++ b/blocks/test/fixtures/core-embedissuu.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedissuu url="https://issuu.com/" -->
-<figure>
+<figure class="wp-block-core-embedissuu">
     https://issuu.com/
     <figcaption>Embedded content from issuu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedkickstarter.html b/blocks/test/fixtures/core-embedkickstarter.html
index dbd11a91fe39b..ca7a645723b3d 100644
--- a/blocks/test/fixtures/core-embedkickstarter.html
+++ b/blocks/test/fixtures/core-embedkickstarter.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedkickstarter url="https://kickstarter.com/" -->
-<figure>
+<figure class="wp-block-core-embedkickstarter">
     https://kickstarter.com/
     <figcaption>Embedded content from kickstarter</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedkickstarter.serialized.html b/blocks/test/fixtures/core-embedkickstarter.serialized.html
index 600c019a80342..a3820965b1c84 100644
--- a/blocks/test/fixtures/core-embedkickstarter.serialized.html
+++ b/blocks/test/fixtures/core-embedkickstarter.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedkickstarter url="https://kickstarter.com/" -->
-<figure>
+<figure class="wp-block-core-embedkickstarter">
     https://kickstarter.com/
     <figcaption>Embedded content from kickstarter</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmeetupcom.html b/blocks/test/fixtures/core-embedmeetupcom.html
index f72f0acfcea7e..e70d7742dc7fb 100644
--- a/blocks/test/fixtures/core-embedmeetupcom.html
+++ b/blocks/test/fixtures/core-embedmeetupcom.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmeetupcom url="https://meetupcom.com/" -->
-<figure>
+<figure class="wp-block-core-embedmeetupcom">
     https://meetupcom.com/
     <figcaption>Embedded content from meetupcom</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmeetupcom.serialized.html b/blocks/test/fixtures/core-embedmeetupcom.serialized.html
index c271a0550b38c..8d10823d4308c 100644
--- a/blocks/test/fixtures/core-embedmeetupcom.serialized.html
+++ b/blocks/test/fixtures/core-embedmeetupcom.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmeetupcom url="https://meetupcom.com/" -->
-<figure>
+<figure class="wp-block-core-embedmeetupcom">
     https://meetupcom.com/
     <figcaption>Embedded content from meetupcom</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmixcloud.html b/blocks/test/fixtures/core-embedmixcloud.html
index bf79ac8537924..3df7723847355 100644
--- a/blocks/test/fixtures/core-embedmixcloud.html
+++ b/blocks/test/fixtures/core-embedmixcloud.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmixcloud url="https://mixcloud.com/" -->
-<figure>
+<figure class="wp-block-core-embedmixcloud">
     https://mixcloud.com/
     <figcaption>Embedded content from mixcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmixcloud.serialized.html b/blocks/test/fixtures/core-embedmixcloud.serialized.html
index dd53c339d93a0..25c977a86e271 100644
--- a/blocks/test/fixtures/core-embedmixcloud.serialized.html
+++ b/blocks/test/fixtures/core-embedmixcloud.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmixcloud url="https://mixcloud.com/" -->
-<figure>
+<figure class="wp-block-core-embedmixcloud">
     https://mixcloud.com/
     <figcaption>Embedded content from mixcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedphotobucket.html b/blocks/test/fixtures/core-embedphotobucket.html
index ba8170950c372..cd884bef1ce07 100644
--- a/blocks/test/fixtures/core-embedphotobucket.html
+++ b/blocks/test/fixtures/core-embedphotobucket.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedphotobucket url="https://photobucket.com/" -->
-<figure>
+<figure class="wp-block-core-embedphotobucket">
     https://photobucket.com/
     <figcaption>Embedded content from photobucket</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedphotobucket.serialized.html b/blocks/test/fixtures/core-embedphotobucket.serialized.html
index e2631ab04ceee..ddf81880fdf2e 100644
--- a/blocks/test/fixtures/core-embedphotobucket.serialized.html
+++ b/blocks/test/fixtures/core-embedphotobucket.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedphotobucket url="https://photobucket.com/" -->
-<figure>
+<figure class="wp-block-core-embedphotobucket">
     https://photobucket.com/
     <figcaption>Embedded content from photobucket</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedpolldaddy.html b/blocks/test/fixtures/core-embedpolldaddy.html
index 4176efd62628d..508aba1c396fe 100644
--- a/blocks/test/fixtures/core-embedpolldaddy.html
+++ b/blocks/test/fixtures/core-embedpolldaddy.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedpolldaddy url="https://polldaddy.com/" -->
-<figure>
+<figure class="wp-block-core-embedpolldaddy">
     https://polldaddy.com/
     <figcaption>Embedded content from polldaddy</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedpolldaddy.serialized.html b/blocks/test/fixtures/core-embedpolldaddy.serialized.html
index 20f6eba0732f3..4d8cbb5f91af0 100644
--- a/blocks/test/fixtures/core-embedpolldaddy.serialized.html
+++ b/blocks/test/fixtures/core-embedpolldaddy.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedpolldaddy url="https://polldaddy.com/" -->
-<figure>
+<figure class="wp-block-core-embedpolldaddy">
     https://polldaddy.com/
     <figcaption>Embedded content from polldaddy</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreddit.html b/blocks/test/fixtures/core-embedreddit.html
index 3537909ad8430..2b083415c3b61 100644
--- a/blocks/test/fixtures/core-embedreddit.html
+++ b/blocks/test/fixtures/core-embedreddit.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreddit url="https://reddit.com/" -->
-<figure>
+<figure class="wp-block-core-embedreddit">
     https://reddit.com/
     <figcaption>Embedded content from reddit</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreddit.serialized.html b/blocks/test/fixtures/core-embedreddit.serialized.html
index 8fda9380fb209..ec9e894c51185 100644
--- a/blocks/test/fixtures/core-embedreddit.serialized.html
+++ b/blocks/test/fixtures/core-embedreddit.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreddit url="https://reddit.com/" -->
-<figure>
+<figure class="wp-block-core-embedreddit">
     https://reddit.com/
     <figcaption>Embedded content from reddit</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreverbnation.html b/blocks/test/fixtures/core-embedreverbnation.html
index 3e03c3404f757..36923f77f1035 100644
--- a/blocks/test/fixtures/core-embedreverbnation.html
+++ b/blocks/test/fixtures/core-embedreverbnation.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreverbnation url="https://reverbnation.com/" -->
-<figure>
+<figure class="wp-block-core-embedreverbnation">
     https://reverbnation.com/
     <figcaption>Embedded content from reverbnation</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreverbnation.serialized.html b/blocks/test/fixtures/core-embedreverbnation.serialized.html
index 3f5686dad96cf..7482ef1e1604b 100644
--- a/blocks/test/fixtures/core-embedreverbnation.serialized.html
+++ b/blocks/test/fixtures/core-embedreverbnation.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreverbnation url="https://reverbnation.com/" -->
-<figure>
+<figure class="wp-block-core-embedreverbnation">
     https://reverbnation.com/
     <figcaption>Embedded content from reverbnation</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscreencast.html b/blocks/test/fixtures/core-embedscreencast.html
index 75e7990c480f7..5f7a10844a7ce 100644
--- a/blocks/test/fixtures/core-embedscreencast.html
+++ b/blocks/test/fixtures/core-embedscreencast.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscreencast url="https://screencast.com/" -->
-<figure>
+<figure class="wp-block-core-embedscreencast">
     https://screencast.com/
     <figcaption>Embedded content from screencast</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscreencast.serialized.html b/blocks/test/fixtures/core-embedscreencast.serialized.html
index 2d6b546863769..efea68a484219 100644
--- a/blocks/test/fixtures/core-embedscreencast.serialized.html
+++ b/blocks/test/fixtures/core-embedscreencast.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscreencast url="https://screencast.com/" -->
-<figure>
+<figure class="wp-block-core-embedscreencast">
     https://screencast.com/
     <figcaption>Embedded content from screencast</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscribd.html b/blocks/test/fixtures/core-embedscribd.html
index 4971e8c943842..a4872f0920b6b 100644
--- a/blocks/test/fixtures/core-embedscribd.html
+++ b/blocks/test/fixtures/core-embedscribd.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscribd url="https://scribd.com/" -->
-<figure>
+<figure class="wp-block-core-embedscribd">
     https://scribd.com/
     <figcaption>Embedded content from scribd</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscribd.serialized.html b/blocks/test/fixtures/core-embedscribd.serialized.html
index 06069125228bd..d1a1fb5e94167 100644
--- a/blocks/test/fixtures/core-embedscribd.serialized.html
+++ b/blocks/test/fixtures/core-embedscribd.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscribd url="https://scribd.com/" -->
-<figure>
+<figure class="wp-block-core-embedscribd">
     https://scribd.com/
     <figcaption>Embedded content from scribd</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedslideshare.html b/blocks/test/fixtures/core-embedslideshare.html
index abd33acdf7c46..ae29ae9b10857 100644
--- a/blocks/test/fixtures/core-embedslideshare.html
+++ b/blocks/test/fixtures/core-embedslideshare.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedslideshare url="https://slideshare.com/" -->
-<figure>
+<figure class="wp-block-core-embedslideshare">
     https://slideshare.com/
     <figcaption>Embedded content from slideshare</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedslideshare.serialized.html b/blocks/test/fixtures/core-embedslideshare.serialized.html
index 8184fc98e5a1a..89ad51a722de8 100644
--- a/blocks/test/fixtures/core-embedslideshare.serialized.html
+++ b/blocks/test/fixtures/core-embedslideshare.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedslideshare url="https://slideshare.com/" -->
-<figure>
+<figure class="wp-block-core-embedslideshare">
     https://slideshare.com/
     <figcaption>Embedded content from slideshare</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsmugmug.html b/blocks/test/fixtures/core-embedsmugmug.html
index 7dc99c1cb7dfb..a778508749c0a 100644
--- a/blocks/test/fixtures/core-embedsmugmug.html
+++ b/blocks/test/fixtures/core-embedsmugmug.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsmugmug url="https://smugmug.com/" -->
-<figure>
+<figure class="wp-block-core-embedsmugmug">
     https://smugmug.com/
     <figcaption>Embedded content from smugmug</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsmugmug.serialized.html b/blocks/test/fixtures/core-embedsmugmug.serialized.html
index 4755f4de1a2c5..ae83583b91075 100644
--- a/blocks/test/fixtures/core-embedsmugmug.serialized.html
+++ b/blocks/test/fixtures/core-embedsmugmug.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsmugmug url="https://smugmug.com/" -->
-<figure>
+<figure class="wp-block-core-embedsmugmug">
     https://smugmug.com/
     <figcaption>Embedded content from smugmug</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsoundcloud.html b/blocks/test/fixtures/core-embedsoundcloud.html
index c02c19b249a0b..3bc156f303e82 100644
--- a/blocks/test/fixtures/core-embedsoundcloud.html
+++ b/blocks/test/fixtures/core-embedsoundcloud.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsoundcloud url="https://soundcloud.com/" -->
-<figure>
+<figure class="wp-block-core-embedsoundcloud">
     https://soundcloud.com/
     <figcaption>Embedded content from soundcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsoundcloud.serialized.html b/blocks/test/fixtures/core-embedsoundcloud.serialized.html
index 70688f2cad848..0edbe298420f7 100644
--- a/blocks/test/fixtures/core-embedsoundcloud.serialized.html
+++ b/blocks/test/fixtures/core-embedsoundcloud.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsoundcloud url="https://soundcloud.com/" -->
-<figure>
+<figure class="wp-block-core-embedsoundcloud">
     https://soundcloud.com/
     <figcaption>Embedded content from soundcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspeaker.html b/blocks/test/fixtures/core-embedspeaker.html
index a7a9332fff5d2..77aec2c0c2d99 100644
--- a/blocks/test/fixtures/core-embedspeaker.html
+++ b/blocks/test/fixtures/core-embedspeaker.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspeaker url="https://speaker.com/" -->
-<figure>
+<figure class="wp-block-core-embedspeaker">
     https://speaker.com/
     <figcaption>Embedded content from speaker</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspeaker.serialized.html b/blocks/test/fixtures/core-embedspeaker.serialized.html
index 77b6efdd62940..5c880c62d7589 100644
--- a/blocks/test/fixtures/core-embedspeaker.serialized.html
+++ b/blocks/test/fixtures/core-embedspeaker.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspeaker url="https://speaker.com/" -->
-<figure>
+<figure class="wp-block-core-embedspeaker">
     https://speaker.com/
     <figcaption>Embedded content from speaker</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspotify.html b/blocks/test/fixtures/core-embedspotify.html
index bfe67cb9034fc..cae29199f19c1 100644
--- a/blocks/test/fixtures/core-embedspotify.html
+++ b/blocks/test/fixtures/core-embedspotify.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspotify url="https://spotify.com/" -->
-<figure>
+<figure class="wp-block-core-embedspotify">
     https://spotify.com/
     <figcaption>Embedded content from spotify</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspotify.serialized.html b/blocks/test/fixtures/core-embedspotify.serialized.html
index 8e88da9f4e3a2..13ca4f3798771 100644
--- a/blocks/test/fixtures/core-embedspotify.serialized.html
+++ b/blocks/test/fixtures/core-embedspotify.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspotify url="https://spotify.com/" -->
-<figure>
+<figure class="wp-block-core-embedspotify">
     https://spotify.com/
     <figcaption>Embedded content from spotify</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedted.html b/blocks/test/fixtures/core-embedted.html
index eb58f0c2c3949..2546b6d74bd31 100644
--- a/blocks/test/fixtures/core-embedted.html
+++ b/blocks/test/fixtures/core-embedted.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedted url="https://ted.com/" -->
-<figure>
+<figure class="wp-block-core-embedted">
     https://ted.com/
     <figcaption>Embedded content from ted</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedted.serialized.html b/blocks/test/fixtures/core-embedted.serialized.html
index 5a9d51536f5da..638848a4cada2 100644
--- a/blocks/test/fixtures/core-embedted.serialized.html
+++ b/blocks/test/fixtures/core-embedted.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedted url="https://ted.com/" -->
-<figure>
+<figure class="wp-block-core-embedted">
     https://ted.com/
     <figcaption>Embedded content from ted</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtumblr.html b/blocks/test/fixtures/core-embedtumblr.html
index ee07d48e887ba..0a1fc1a1292bb 100644
--- a/blocks/test/fixtures/core-embedtumblr.html
+++ b/blocks/test/fixtures/core-embedtumblr.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtumblr url="https://tumblr.com/" -->
-<figure>
+<figure class="wp-block-core-embedtumblr">
     https://tumblr.com/
     <figcaption>Embedded content from tumblr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtumblr.serialized.html b/blocks/test/fixtures/core-embedtumblr.serialized.html
index 8f1da3fb2e4d9..b31aa5ad8714b 100644
--- a/blocks/test/fixtures/core-embedtumblr.serialized.html
+++ b/blocks/test/fixtures/core-embedtumblr.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtumblr url="https://tumblr.com/" -->
-<figure>
+<figure class="wp-block-core-embedtumblr">
     https://tumblr.com/
     <figcaption>Embedded content from tumblr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtwitter.html b/blocks/test/fixtures/core-embedtwitter.html
index 807a6bfd27604..14604151a39ea 100644
--- a/blocks/test/fixtures/core-embedtwitter.html
+++ b/blocks/test/fixtures/core-embedtwitter.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtwitter url="https://twitter.com/automattic" -->
-<figure>
+<figure class="wp-block-core-embedtwitter">
     https://twitter.com/automattic
     <figcaption>We are Automattic</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtwitter.serialized.html b/blocks/test/fixtures/core-embedtwitter.serialized.html
index bc214e661e01e..d959f9f76912b 100644
--- a/blocks/test/fixtures/core-embedtwitter.serialized.html
+++ b/blocks/test/fixtures/core-embedtwitter.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtwitter url="https://twitter.com/automattic" -->
-<figure>
+<figure class="wp-block-core-embedtwitter">
     https://twitter.com/automattic
     <figcaption>We are Automattic</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvideopress.html b/blocks/test/fixtures/core-embedvideopress.html
index ba2ff6bdc2e51..852ca78e203f0 100644
--- a/blocks/test/fixtures/core-embedvideopress.html
+++ b/blocks/test/fixtures/core-embedvideopress.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvideopress url="https://videopress.com/" -->
-<figure>
+<figure class="wp-block-core-embedvideopress">
     https://videopress.com/
     <figcaption>Embedded content from videopress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvideopress.serialized.html b/blocks/test/fixtures/core-embedvideopress.serialized.html
index 571972d53ff4d..5ad3deaeae761 100644
--- a/blocks/test/fixtures/core-embedvideopress.serialized.html
+++ b/blocks/test/fixtures/core-embedvideopress.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvideopress url="https://videopress.com/" -->
-<figure>
+<figure class="wp-block-core-embedvideopress">
     https://videopress.com/
     <figcaption>Embedded content from videopress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvimeo.html b/blocks/test/fixtures/core-embedvimeo.html
index 81b4698f749c2..3e3ecf54288a9 100644
--- a/blocks/test/fixtures/core-embedvimeo.html
+++ b/blocks/test/fixtures/core-embedvimeo.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvimeo url="https://vimeo.com/" -->
-<figure>
+<figure class="wp-block-core-embedvimeo">
     https://vimeo.com/
     <figcaption>Embedded content from vimeo</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvimeo.serialized.html b/blocks/test/fixtures/core-embedvimeo.serialized.html
index eb1522a937aea..c23c39d52ad4f 100644
--- a/blocks/test/fixtures/core-embedvimeo.serialized.html
+++ b/blocks/test/fixtures/core-embedvimeo.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvimeo url="https://vimeo.com/" -->
-<figure>
+<figure class="wp-block-core-embedvimeo">
     https://vimeo.com/
     <figcaption>Embedded content from vimeo</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvine.html b/blocks/test/fixtures/core-embedvine.html
index b70558a5fc77b..e7ed0d2f98847 100644
--- a/blocks/test/fixtures/core-embedvine.html
+++ b/blocks/test/fixtures/core-embedvine.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvine url="https://vine.com/" -->
-<figure>
+<figure class="wp-block-core-embedvine">
     https://vine.com/
     <figcaption>Embedded content from vine</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvine.serialized.html b/blocks/test/fixtures/core-embedvine.serialized.html
index df9496fb94081..23877d1ece71c 100644
--- a/blocks/test/fixtures/core-embedvine.serialized.html
+++ b/blocks/test/fixtures/core-embedvine.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvine url="https://vine.com/" -->
-<figure>
+<figure class="wp-block-core-embedvine">
     https://vine.com/
     <figcaption>Embedded content from vine</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpress.html b/blocks/test/fixtures/core-embedwordpress.html
index accd979b51f83..e16386905c58a 100644
--- a/blocks/test/fixtures/core-embedwordpress.html
+++ b/blocks/test/fixtures/core-embedwordpress.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpress url="https://wordpress.com/" -->
-<figure>
+<figure class="wp-block-core-embedwordpress">
     https://wordpress.com/
     <figcaption>Embedded content from WordPress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpress.serialized.html b/blocks/test/fixtures/core-embedwordpress.serialized.html
index 0905c1b166b45..9748cc91b9e3b 100644
--- a/blocks/test/fixtures/core-embedwordpress.serialized.html
+++ b/blocks/test/fixtures/core-embedwordpress.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpress url="https://wordpress.com/" -->
-<figure>
+<figure class="wp-block-core-embedwordpress">
     https://wordpress.com/
     <figcaption>Embedded content from WordPress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpresstv.html b/blocks/test/fixtures/core-embedwordpresstv.html
index eca3877f5ced8..3675fe56b6f5d 100644
--- a/blocks/test/fixtures/core-embedwordpresstv.html
+++ b/blocks/test/fixtures/core-embedwordpresstv.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpresstv url="https://wordpresstv.com/" -->
-<figure>
+<figure class="wp-block-core-embedwordpresstv">
     https://wordpresstv.com/
     <figcaption>Embedded content from wordpresstv</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpresstv.serialized.html b/blocks/test/fixtures/core-embedwordpresstv.serialized.html
index bc6c773f16293..a906d563357c0 100644
--- a/blocks/test/fixtures/core-embedwordpresstv.serialized.html
+++ b/blocks/test/fixtures/core-embedwordpresstv.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpresstv url="https://wordpresstv.com/" -->
-<figure>
+<figure class="wp-block-core-embedwordpresstv">
     https://wordpresstv.com/
     <figcaption>Embedded content from wordpresstv</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedyoutube.html b/blocks/test/fixtures/core-embedyoutube.html
index e0832c00589d2..b97d4fa9c7a34 100644
--- a/blocks/test/fixtures/core-embedyoutube.html
+++ b/blocks/test/fixtures/core-embedyoutube.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedyoutube url="https://youtube.com/" -->
-<figure>
+<figure class="wp-block-core-embedyoutube">
     https://youtube.com/
     <figcaption>Embedded content from youtube</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedyoutube.serialized.html b/blocks/test/fixtures/core-embedyoutube.serialized.html
index 02fa086d489e7..f5ed0ba74ddf9 100644
--- a/blocks/test/fixtures/core-embedyoutube.serialized.html
+++ b/blocks/test/fixtures/core-embedyoutube.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedyoutube url="https://youtube.com/" -->
-<figure>
+<figure class="wp-block-core-embedyoutube">
     https://youtube.com/
     <figcaption>Embedded content from youtube</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-freeform.serialized.html b/blocks/test/fixtures/core-freeform.serialized.html
index d30114895dd4c..e603f3513a0dd 100644
--- a/blocks/test/fixtures/core-freeform.serialized.html
+++ b/blocks/test/fixtures/core-freeform.serialized.html
@@ -1,6 +1,6 @@
 <!-- wp:core/freeform -->
 Testing freeform block with some
-<div class="wp-some-class">
+<div class="wp-some-class wp-block-core-freeform">
     HTML <span style="color:red;">content</span>
 </div>
 <!-- /wp:core/freeform -->
diff --git a/blocks/test/fixtures/core-gallery.html b/blocks/test/fixtures/core-gallery.html
index 523a6732dd959..d313804cbb125 100644
--- a/blocks/test/fixtures/core-gallery.html
+++ b/blocks/test/fixtures/core-gallery.html
@@ -1,5 +1,5 @@
 <!-- wp:core/gallery -->
-<div class="blocks-gallery">
+<div class="blocks-gallery wp-block-core-gallery">
 	<figure class="blocks-gallery-image">
 		<img src="https://cldup.com/uuUqE_dXzy.jpg" alt="title" />
 	</figure>
diff --git a/blocks/test/fixtures/core-gallery.serialized.html b/blocks/test/fixtures/core-gallery.serialized.html
index 09f55993d4fd9..eaf79d8e492be 100644
--- a/blocks/test/fixtures/core-gallery.serialized.html
+++ b/blocks/test/fixtures/core-gallery.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/gallery -->
-<div class="blocks-gallery alignnone columns-2">
+<div class="blocks-gallery alignnone columns-2 wp-block-core-gallery">
     <figure class="blocks-gallery-image"><img src="https://cldup.com/uuUqE_dXzy.jpg" alt="title" /></figure>
     <figure class="blocks-gallery-image"><img src="http://google.com/hi.png" alt="title" /></figure>
 </div>
diff --git a/blocks/test/fixtures/core-heading-h2-em.html b/blocks/test/fixtures/core-heading-h2-em.html
index 7755d1dcf4eae..38394de2ad218 100644
--- a/blocks/test/fixtures/core-heading-h2-em.html
+++ b/blocks/test/fixtures/core-heading-h2-em.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading -->
-<h2>The <em>Inserter</em> Tool</h2>
+<h2 class="wp-block-core-heading">The <em>Inserter</em> Tool</h2>
 <!-- /wp:core/heading -->
diff --git a/blocks/test/fixtures/core-heading-h2-em.serialized.html b/blocks/test/fixtures/core-heading-h2-em.serialized.html
index e45d45e05d4ee..d8f0267a69ab5 100644
--- a/blocks/test/fixtures/core-heading-h2-em.serialized.html
+++ b/blocks/test/fixtures/core-heading-h2-em.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/heading -->
-<h2>The <em>Inserter</em> Tool</h2>
+<h2 class="wp-block-core-heading">The <em>Inserter</em> Tool</h2>
 <!-- /wp:core/heading -->
 
diff --git a/blocks/test/fixtures/core-heading-h2.html b/blocks/test/fixtures/core-heading-h2.html
index a55b391a25057..c9baba90b8186 100644
--- a/blocks/test/fixtures/core-heading-h2.html
+++ b/blocks/test/fixtures/core-heading-h2.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading -->
-<h2>A picture is worth a thousand words, or so the saying goes</h2>
+<h2 class="wp-block-core-heading">A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:core/heading -->
diff --git a/blocks/test/fixtures/core-heading-h2.serialized.html b/blocks/test/fixtures/core-heading-h2.serialized.html
index 180f05ff62466..db488794ad4f2 100644
--- a/blocks/test/fixtures/core-heading-h2.serialized.html
+++ b/blocks/test/fixtures/core-heading-h2.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/heading -->
-<h2>A picture is worth a thousand words, or so the saying goes</h2>
+<h2 class="wp-block-core-heading">A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:core/heading -->
 
diff --git a/blocks/test/fixtures/core-image-center-caption.html b/blocks/test/fixtures/core-image-center-caption.html
index a528bacf46745..5a4b63a0b35a6 100644
--- a/blocks/test/fixtures/core-image-center-caption.html
+++ b/blocks/test/fixtures/core-image-center-caption.html
@@ -1,3 +1,3 @@
 <!-- wp:core/image align="center" -->
-<figure><img src="https://cldup.com/YLYhpou2oq.jpg" class="aligncenter"/><figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption></figure>
+<figure class="wp-block-core-image"><img src="https://cldup.com/YLYhpou2oq.jpg" class="aligncenter"/><figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption></figure>
 <!-- /wp:core/image -->
diff --git a/blocks/test/fixtures/core-image-center-caption.serialized.html b/blocks/test/fixtures/core-image-center-caption.serialized.html
index 0e3edecb381cb..db8452ea131fc 100644
--- a/blocks/test/fixtures/core-image-center-caption.serialized.html
+++ b/blocks/test/fixtures/core-image-center-caption.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/image align="center" -->
-<figure class="aligncenter"><img src="https://cldup.com/YLYhpou2oq.jpg" />
+<figure class="aligncenter wp-block-core-image"><img src="https://cldup.com/YLYhpou2oq.jpg" />
     <figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption>
 </figure>
 <!-- /wp:core/image -->
diff --git a/blocks/test/fixtures/core-image.html b/blocks/test/fixtures/core-image.html
index 7ca7dd87f9f01..42bdd73fca695 100644
--- a/blocks/test/fixtures/core-image.html
+++ b/blocks/test/fixtures/core-image.html
@@ -1,3 +1,3 @@
 <!-- wp:core/image -->
-<figure><img src="https://cldup.com/uuUqE_dXzy.jpg" /></figure>
+<figure class="wp-block-core-image"><img src="https://cldup.com/uuUqE_dXzy.jpg" /></figure>
 <!-- /wp:core/image -->
diff --git a/blocks/test/fixtures/core-image.serialized.html b/blocks/test/fixtures/core-image.serialized.html
index 2b27696131025..d4050b47a8121 100644
--- a/blocks/test/fixtures/core-image.serialized.html
+++ b/blocks/test/fixtures/core-image.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/image -->
-<img src="https://cldup.com/uuUqE_dXzy.jpg" class="alignnone" />
+<img src="https://cldup.com/uuUqE_dXzy.jpg" class="alignnone wp-block-core-image" />
 <!-- /wp:core/image -->
 
diff --git a/blocks/test/fixtures/core-list-ul.html b/blocks/test/fixtures/core-list-ul.html
index aef6bf669f2c9..1af7352863290 100644
--- a/blocks/test/fixtures/core-list-ul.html
+++ b/blocks/test/fixtures/core-list-ul.html
@@ -1,3 +1,3 @@
 <!-- wp:core/list -->
-<ul><li>Text & Headings</li><li>Images & Videos</li><li>Galleries</li><li>Embeds, like YouTube, Tweets, or other WordPress posts.</li><li>Layout blocks, like Buttons, Hero Images, Separators, etc.</li><li>And <em>Lists</em> like this one of course :)</li></ul>
+<ul class="wp-block-core-list"><li>Text & Headings</li><li>Images & Videos</li><li>Galleries</li><li>Embeds, like YouTube, Tweets, or other WordPress posts.</li><li>Layout blocks, like Buttons, Hero Images, Separators, etc.</li><li>And <em>Lists</em> like this one of course :)</li></ul>
 <!-- /wp:core/list -->
diff --git a/blocks/test/fixtures/core-list-ul.serialized.html b/blocks/test/fixtures/core-list-ul.serialized.html
index f572f8fc37b11..8386d37b0ad9a 100644
--- a/blocks/test/fixtures/core-list-ul.serialized.html
+++ b/blocks/test/fixtures/core-list-ul.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/list -->
-<ul>
+<ul class="wp-block-core-list">
     <li>Text &amp; Headings</li>
     <li>Images &amp; Videos</li>
     <li>Galleries</li>
diff --git a/blocks/test/fixtures/core-preformatted.html b/blocks/test/fixtures/core-preformatted.html
index 1b3abc31853c0..820c5eed8a096 100644
--- a/blocks/test/fixtures/core-preformatted.html
+++ b/blocks/test/fixtures/core-preformatted.html
@@ -1,3 +1,3 @@
 <!-- wp:core/preformatted -->
-<pre>Some <em>preformatted</em> text...<br>And more!</pre>
+<pre class="wp-block-core-preformatted">Some <em>preformatted</em> text...<br>And more!</pre>
 <!-- /wp:core/preformatted -->
diff --git a/blocks/test/fixtures/core-preformatted.serialized.html b/blocks/test/fixtures/core-preformatted.serialized.html
index b119b914cf0e4..cf82d1da30d94 100644
--- a/blocks/test/fixtures/core-preformatted.serialized.html
+++ b/blocks/test/fixtures/core-preformatted.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/preformatted -->
-<pre>Some <em>preformatted</em> text...<br/>And more!</pre>
+<pre class="wp-block-core-preformatted">Some <em>preformatted</em> text...<br/>And more!</pre>
 <!-- /wp:core/preformatted -->
 
diff --git a/blocks/test/fixtures/core-pullquote.html b/blocks/test/fixtures/core-pullquote.html
index 027188bce2960..8bb7a431b413a 100644
--- a/blocks/test/fixtures/core-pullquote.html
+++ b/blocks/test/fixtures/core-pullquote.html
@@ -1,5 +1,5 @@
 <!-- wp:core/pullquote -->
-<blockquote class="blocks-pullquote">
+<blockquote class="blocks-pullquote wp-block-core-pullquote">
 <p>Testing pullquote block...</p><footer>...with a caption</footer>
 </blockquote>
 <!-- /wp:core/pullquote -->
diff --git a/blocks/test/fixtures/core-pullquote.serialized.html b/blocks/test/fixtures/core-pullquote.serialized.html
index 741f2d36a2df2..81f69727fac92 100644
--- a/blocks/test/fixtures/core-pullquote.serialized.html
+++ b/blocks/test/fixtures/core-pullquote.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/pullquote -->
-<blockquote class="blocks-pullquote alignnone">
+<blockquote class="blocks-pullquote alignnone wp-block-core-pullquote">
     <p>Testing pullquote block...</p>
     <footer>...with a caption</footer>
 </blockquote>
diff --git a/blocks/test/fixtures/core-quote-style-1.html b/blocks/test/fixtures/core-quote-style-1.html
index e8c9add2748c6..5a57c31317c84 100644
--- a/blocks/test/fixtures/core-quote-style-1.html
+++ b/blocks/test/fixtures/core-quote-style-1.html
@@ -1,3 +1,3 @@
 <!-- wp:core/quote style="1" -->
-<blockquote class="blocks-quote-style-1"><p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p><footer>Matt Mullenweg, 2017</footer></blockquote>
+<blockquote class="blocks-quote-style-1 wp-block-core-quote"><p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p><footer>Matt Mullenweg, 2017</footer></blockquote>
 <!-- /wp:core/quote -->
diff --git a/blocks/test/fixtures/core-quote-style-1.serialized.html b/blocks/test/fixtures/core-quote-style-1.serialized.html
index e38001b88f29a..cc81c868f7bcd 100644
--- a/blocks/test/fixtures/core-quote-style-1.serialized.html
+++ b/blocks/test/fixtures/core-quote-style-1.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/quote style="1" -->
-<blockquote class="blocks-quote-style-1">
+<blockquote class="blocks-quote-style-1 wp-block-core-quote">
     <p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p>
     <footer>Matt Mullenweg, 2017</footer>
 </blockquote>
diff --git a/blocks/test/fixtures/core-quote-style-2.html b/blocks/test/fixtures/core-quote-style-2.html
index b8c255beee8fe..09f9416597e4f 100644
--- a/blocks/test/fixtures/core-quote-style-2.html
+++ b/blocks/test/fixtures/core-quote-style-2.html
@@ -1,3 +1,3 @@
 <!-- wp:core/quote style="2" -->
-<blockquote class="blocks-quote-style-2"><p>There is no greater agony than bearing an untold story inside you.</p><footer>Maya Angelou</footer></blockquote>
+<blockquote class="blocks-quote-style-2 wp-block-core-quote"><p>There is no greater agony than bearing an untold story inside you.</p><footer>Maya Angelou</footer></blockquote>
 <!-- /wp:core/quote -->
diff --git a/blocks/test/fixtures/core-quote-style-2.serialized.html b/blocks/test/fixtures/core-quote-style-2.serialized.html
index 6d5b9988eb347..7a0c8090065be 100644
--- a/blocks/test/fixtures/core-quote-style-2.serialized.html
+++ b/blocks/test/fixtures/core-quote-style-2.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/quote style="2" -->
-<blockquote class="blocks-quote-style-2">
+<blockquote class="blocks-quote-style-2 wp-block-core-quote">
     <p>There is no greater agony than bearing an untold story inside you.</p>
     <footer>Maya Angelou</footer>
 </blockquote>
diff --git a/blocks/test/fixtures/core-separator.html b/blocks/test/fixtures/core-separator.html
index a241e07204f9a..e3e01dd1d028e 100644
--- a/blocks/test/fixtures/core-separator.html
+++ b/blocks/test/fixtures/core-separator.html
@@ -1,3 +1,3 @@
 <!-- wp:core/separator -->
-<hr/>
+<hr class="wp-block-core-separator" />
 <!-- /wp:core/separator -->
diff --git a/blocks/test/fixtures/core-separator.serialized.html b/blocks/test/fixtures/core-separator.serialized.html
index a411529200442..322c9b6a52f30 100644
--- a/blocks/test/fixtures/core-separator.serialized.html
+++ b/blocks/test/fixtures/core-separator.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/separator -->
-<hr/>
+<hr class="wp-block-core-separator" />
 <!-- /wp:core/separator -->
 
diff --git a/blocks/test/fixtures/core-table.html b/blocks/test/fixtures/core-table.html
index 60008a1566ef0..dea1f2fe34ef0 100644
--- a/blocks/test/fixtures/core-table.html
+++ b/blocks/test/fixtures/core-table.html
@@ -1,5 +1,5 @@
 <!-- wp:core/table -->
-<table>
+<table class="wp-block-core-table">
     <thead>
         <tr>
             <th>Version</th>
diff --git a/blocks/test/fixtures/core-table.serialized.html b/blocks/test/fixtures/core-table.serialized.html
index 174adfec5ae84..45e1d6995bb6a 100644
--- a/blocks/test/fixtures/core-table.serialized.html
+++ b/blocks/test/fixtures/core-table.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/table -->
-<table>
+<table class="wp-block-core-table">
     <thead>
         <tr>
             <th>Version</th>
diff --git a/blocks/test/fixtures/core-text-align-right.html b/blocks/test/fixtures/core-text-align-right.html
index d3d0c922ce2bf..878426843f9e1 100644
--- a/blocks/test/fixtures/core-text-align-right.html
+++ b/blocks/test/fixtures/core-text-align-right.html
@@ -1,3 +1,3 @@
 <!-- wp:core/text align="right" -->
-<p style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
+<p class="wp-block-core-text" style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
 <!-- /wp:core/text -->
diff --git a/blocks/test/fixtures/core-text-align-right.serialized.html b/blocks/test/fixtures/core-text-align-right.serialized.html
index 5bbeb051d3186..08cbf1aa903d8 100644
--- a/blocks/test/fixtures/core-text-align-right.serialized.html
+++ b/blocks/test/fixtures/core-text-align-right.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/text align="right" -->
-<p style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
+<p style="text-align:right;" class="wp-block-core-text">... like this one, which is separate from the above and right aligned.</p>
 <!-- /wp:core/text -->
 

From 7592989817e7884c01e3675e534baa49e50dd2b8 Mon Sep 17 00:00:00 2001
From: Riad Benguella <benguella@gmail.com>
Date: Fri, 23 Jun 2017 15:03:42 +0100
Subject: [PATCH 2/7] Serializer: Dropping "-core" from the Core blocks'
 classname

---
 blocks/api/serializer.js                           |  7 ++++++-
 blocks/api/test/serializer.js                      | 14 ++++++++++++--
 blocks/test/fixtures/core-button-center.html       |  2 +-
 .../fixtures/core-button-center.serialized.html    |  2 +-
 blocks/test/fixtures/core-code.html                |  2 +-
 blocks/test/fixtures/core-code.serialized.html     |  2 +-
 blocks/test/fixtures/core-embed.html               |  2 +-
 blocks/test/fixtures/core-embed.serialized.html    |  2 +-
 blocks/test/fixtures/core-embedanimoto.html        |  2 +-
 .../fixtures/core-embedanimoto.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedcloudup.html        |  2 +-
 .../fixtures/core-embedcloudup.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedcollegehumor.html   |  2 +-
 .../core-embedcollegehumor.serialized.html         |  2 +-
 blocks/test/fixtures/core-embeddailymotion.html    |  2 +-
 .../fixtures/core-embeddailymotion.serialized.html |  2 +-
 blocks/test/fixtures/core-embedfacebook.html       |  2 +-
 .../fixtures/core-embedfacebook.serialized.html    |  2 +-
 blocks/test/fixtures/core-embedflickr.html         |  2 +-
 .../test/fixtures/core-embedflickr.serialized.html |  2 +-
 blocks/test/fixtures/core-embedfunnyordie.html     |  2 +-
 .../fixtures/core-embedfunnyordie.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedhulu.html           |  2 +-
 .../test/fixtures/core-embedhulu.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedimgur.html          |  2 +-
 .../test/fixtures/core-embedimgur.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedinstagram.html      |  2 +-
 .../fixtures/core-embedinstagram.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedissuu.html          |  2 +-
 .../test/fixtures/core-embedissuu.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedkickstarter.html    |  2 +-
 .../fixtures/core-embedkickstarter.serialized.html |  2 +-
 blocks/test/fixtures/core-embedmeetupcom.html      |  2 +-
 .../fixtures/core-embedmeetupcom.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedmixcloud.html       |  2 +-
 .../fixtures/core-embedmixcloud.serialized.html    |  2 +-
 blocks/test/fixtures/core-embedphotobucket.html    |  2 +-
 .../fixtures/core-embedphotobucket.serialized.html |  2 +-
 blocks/test/fixtures/core-embedpolldaddy.html      |  2 +-
 .../fixtures/core-embedpolldaddy.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedreddit.html         |  2 +-
 .../test/fixtures/core-embedreddit.serialized.html |  2 +-
 blocks/test/fixtures/core-embedreverbnation.html   |  2 +-
 .../core-embedreverbnation.serialized.html         |  2 +-
 blocks/test/fixtures/core-embedscreencast.html     |  2 +-
 .../fixtures/core-embedscreencast.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedscribd.html         |  2 +-
 .../test/fixtures/core-embedscribd.serialized.html |  2 +-
 blocks/test/fixtures/core-embedslideshare.html     |  2 +-
 .../fixtures/core-embedslideshare.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedsmugmug.html        |  2 +-
 .../fixtures/core-embedsmugmug.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedsoundcloud.html     |  2 +-
 .../fixtures/core-embedsoundcloud.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedspeaker.html        |  2 +-
 .../fixtures/core-embedspeaker.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedspotify.html        |  2 +-
 .../fixtures/core-embedspotify.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedted.html            |  2 +-
 blocks/test/fixtures/core-embedted.serialized.html |  2 +-
 blocks/test/fixtures/core-embedtumblr.html         |  2 +-
 .../test/fixtures/core-embedtumblr.serialized.html |  2 +-
 blocks/test/fixtures/core-embedtwitter.html        |  2 +-
 .../fixtures/core-embedtwitter.serialized.html     |  2 +-
 blocks/test/fixtures/core-embedvideopress.html     |  2 +-
 .../fixtures/core-embedvideopress.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedvimeo.html          |  2 +-
 .../test/fixtures/core-embedvimeo.serialized.html  |  2 +-
 blocks/test/fixtures/core-embedvine.html           |  2 +-
 .../test/fixtures/core-embedvine.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedwordpress.html      |  2 +-
 .../fixtures/core-embedwordpress.serialized.html   |  2 +-
 blocks/test/fixtures/core-embedwordpresstv.html    |  2 +-
 .../fixtures/core-embedwordpresstv.serialized.html |  2 +-
 blocks/test/fixtures/core-embedyoutube.html        |  2 +-
 .../fixtures/core-embedyoutube.serialized.html     |  2 +-
 blocks/test/fixtures/core-freeform.serialized.html |  2 +-
 blocks/test/fixtures/core-gallery.html             |  2 +-
 blocks/test/fixtures/core-gallery.serialized.html  |  2 +-
 blocks/test/fixtures/core-heading-h2-em.html       |  2 +-
 .../fixtures/core-heading-h2-em.serialized.html    |  2 +-
 blocks/test/fixtures/core-heading-h2.html          |  2 +-
 .../test/fixtures/core-heading-h2.serialized.html  |  2 +-
 .../test/fixtures/core-image-center-caption.html   |  2 +-
 .../core-image-center-caption.serialized.html      |  2 +-
 blocks/test/fixtures/core-image.html               |  2 +-
 blocks/test/fixtures/core-image.serialized.html    |  2 +-
 blocks/test/fixtures/core-list-ul.html             |  2 +-
 blocks/test/fixtures/core-list-ul.serialized.html  |  2 +-
 blocks/test/fixtures/core-preformatted.html        |  2 +-
 .../fixtures/core-preformatted.serialized.html     |  2 +-
 blocks/test/fixtures/core-pullquote.html           |  2 +-
 .../test/fixtures/core-pullquote.serialized.html   |  2 +-
 blocks/test/fixtures/core-quote-style-1.html       |  2 +-
 .../fixtures/core-quote-style-1.serialized.html    |  2 +-
 blocks/test/fixtures/core-quote-style-2.html       |  2 +-
 .../fixtures/core-quote-style-2.serialized.html    |  2 +-
 blocks/test/fixtures/core-separator.html           |  2 +-
 .../test/fixtures/core-separator.serialized.html   |  2 +-
 blocks/test/fixtures/core-table.html               |  2 +-
 blocks/test/fixtures/core-table.serialized.html    |  2 +-
 blocks/test/fixtures/core-text-align-right.html    |  2 +-
 .../fixtures/core-text-align-right.serialized.html |  2 +-
 103 files changed, 119 insertions(+), 104 deletions(-)

diff --git a/blocks/api/serializer.js b/blocks/api/serializer.js
index 4991f5b49288c..53cd689e10cc9 100644
--- a/blocks/api/serializer.js
+++ b/blocks/api/serializer.js
@@ -44,7 +44,12 @@ export function getSaveContent( save, blockName, attributes ) {
 		if ( ! element || ! isObject( element ) ) {
 			return element;
 		}
-		const className = classnames( element.props.className, `wp-block-${ kebabCase( blockName ) }` );
+
+		// Drop the namespace "core/"" for core blocks only
+		const match = /^([a-z0-9-]+)\/([a-z0-9-]+)$/.exec( blockName );
+		const sanitizedBlockName = match[ 1 ] === 'core' ? match[ 2 ] : blockName;
+
+		const className = classnames( element.props.className, `wp-block-${ kebabCase( sanitizedBlockName ) }` );
 		return cloneElement( element, { className } );
 	};
 	const contentWithClassname = Children.map( rawContent, addClassnameToElement );
diff --git a/blocks/api/test/serializer.js b/blocks/api/test/serializer.js
index 0b244eba3f803..645f670df4565 100644
--- a/blocks/api/test/serializer.js
+++ b/blocks/api/test/serializer.js
@@ -40,7 +40,17 @@ describe( 'block serializer', () => {
 					{ fruit: 'Bananas' }
 				);
 
-				expect( saved ).to.equal( '<div class="wp-block-core-fruit">Bananas</div>' );
+				expect( saved ).to.equal( '<div class="wp-block-fruit">Bananas</div>' );
+			} );
+
+			it( 'should return use the namespace in the classname if it\' not a core block', () => {
+				const saved = getSaveContent(
+					( { attributes } ) => createElement( 'div', null, attributes.fruit ),
+					'myplugin/fruit',
+					{ fruit: 'Bananas' }
+				);
+
+				expect( saved ).to.equal( '<div class="wp-block-myplugin-fruit">Bananas</div>' );
 			} );
 		} );
 
@@ -127,7 +137,7 @@ describe( 'block serializer', () => {
 					},
 				},
 			];
-			const expectedPostContent = '<!-- wp:core/test-block align="left" -->\n<p class="wp-block-core-test-block">Ribs & Chicken</p>\n<!-- /wp:core/test-block -->';
+			const expectedPostContent = '<!-- wp:core/test-block align="left" -->\n<p class="wp-block-test-block">Ribs & Chicken</p>\n<!-- /wp:core/test-block -->';
 
 			expect( serialize( blockList ) ).to.eql( expectedPostContent );
 		} );
diff --git a/blocks/test/fixtures/core-button-center.html b/blocks/test/fixtures/core-button-center.html
index 312b3532e72e7..9e1899a30fec2 100644
--- a/blocks/test/fixtures/core-button-center.html
+++ b/blocks/test/fixtures/core-button-center.html
@@ -1,3 +1,3 @@
 <!-- wp:core/button align="center" -->
-<div class="aligncenter wp-block-core-button"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
+<div class="aligncenter wp-block-button"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
 <!-- /wp:core/button -->
diff --git a/blocks/test/fixtures/core-button-center.serialized.html b/blocks/test/fixtures/core-button-center.serialized.html
index 971bb48cfc038..d86f39e98c299 100644
--- a/blocks/test/fixtures/core-button-center.serialized.html
+++ b/blocks/test/fixtures/core-button-center.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/button align="center" -->
-<div class="aligncenter wp-block-core-button"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
+<div class="aligncenter wp-block-button"><a href="https://github.com/WordPress/gutenberg">Help build Gutenberg</a></div>
 <!-- /wp:core/button -->
 
diff --git a/blocks/test/fixtures/core-code.html b/blocks/test/fixtures/core-code.html
index bbfc1b5a80f91..5d3f951c17f71 100644
--- a/blocks/test/fixtures/core-code.html
+++ b/blocks/test/fixtures/core-code.html
@@ -1,5 +1,5 @@
 <!-- wp:core/code -->
-<pre class="wp-block-core-code"><code>export default function MyButton() {
+<pre class="wp-block-code"><code>export default function MyButton() {
 	return &lt;Button&gt;Click Me!&lt;/Button&gt;;
 }</code></pre>
 <!-- /wp:core/code -->
diff --git a/blocks/test/fixtures/core-code.serialized.html b/blocks/test/fixtures/core-code.serialized.html
index f74b38be87235..695395457a7c9 100644
--- a/blocks/test/fixtures/core-code.serialized.html
+++ b/blocks/test/fixtures/core-code.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/code -->
-<pre class="wp-block-core-code"><code>export default function MyButton() {
+<pre class="wp-block-code"><code>export default function MyButton() {
 	return &lt;Button&gt;Click Me!&lt;/Button&gt;;
 }</code></pre>
 <!-- /wp:core/code -->
diff --git a/blocks/test/fixtures/core-embed.html b/blocks/test/fixtures/core-embed.html
index a22b8055dbb14..4a3a026dbbfaa 100644
--- a/blocks/test/fixtures/core-embed.html
+++ b/blocks/test/fixtures/core-embed.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embed url="https://example.com/" -->
-<figure class="wp-block-core-embed">
+<figure class="wp-block-embed">
     https://example.com/
     <figcaption>Embedded content from an example URL</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embed.serialized.html b/blocks/test/fixtures/core-embed.serialized.html
index b79ba1e98afb5..3a48b93509de9 100644
--- a/blocks/test/fixtures/core-embed.serialized.html
+++ b/blocks/test/fixtures/core-embed.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embed url="https://example.com/" -->
-<figure class="wp-block-core-embed">
+<figure class="wp-block-embed">
     https://example.com/
     <figcaption>Embedded content from an example URL</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedanimoto.html b/blocks/test/fixtures/core-embedanimoto.html
index 0675dad35eb3b..0b636c81362b2 100644
--- a/blocks/test/fixtures/core-embedanimoto.html
+++ b/blocks/test/fixtures/core-embedanimoto.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedanimoto url="https://animoto.com/" -->
-<figure class="wp-block-core-embedanimoto">
+<figure class="wp-block-embedanimoto">
     https://animoto.com/
     <figcaption>Embedded content from animoto</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedanimoto.serialized.html b/blocks/test/fixtures/core-embedanimoto.serialized.html
index 22508b2fc631d..a007c6b7bedad 100644
--- a/blocks/test/fixtures/core-embedanimoto.serialized.html
+++ b/blocks/test/fixtures/core-embedanimoto.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedanimoto url="https://animoto.com/" -->
-<figure class="wp-block-core-embedanimoto">
+<figure class="wp-block-embedanimoto">
     https://animoto.com/
     <figcaption>Embedded content from animoto</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcloudup.html b/blocks/test/fixtures/core-embedcloudup.html
index 73922f0aecfba..4a9e1505aab67 100644
--- a/blocks/test/fixtures/core-embedcloudup.html
+++ b/blocks/test/fixtures/core-embedcloudup.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcloudup url="https://cloudup.com/" -->
-<figure class="wp-block-core-embedcloudup">
+<figure class="wp-block-embedcloudup">
     https://cloudup.com/
     <figcaption>Embedded content from cloudup</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcloudup.serialized.html b/blocks/test/fixtures/core-embedcloudup.serialized.html
index 5515f4124b29e..fda04d9fc6808 100644
--- a/blocks/test/fixtures/core-embedcloudup.serialized.html
+++ b/blocks/test/fixtures/core-embedcloudup.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcloudup url="https://cloudup.com/" -->
-<figure class="wp-block-core-embedcloudup">
+<figure class="wp-block-embedcloudup">
     https://cloudup.com/
     <figcaption>Embedded content from cloudup</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcollegehumor.html b/blocks/test/fixtures/core-embedcollegehumor.html
index 1667705e6b095..7cc4683fbd3b6 100644
--- a/blocks/test/fixtures/core-embedcollegehumor.html
+++ b/blocks/test/fixtures/core-embedcollegehumor.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcollegehumor url="https://collegehumor.com/" -->
-<figure class="wp-block-core-embedcollegehumor">
+<figure class="wp-block-embedcollegehumor">
     https://collegehumor.com/
     <figcaption>Embedded content from collegehumor</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedcollegehumor.serialized.html b/blocks/test/fixtures/core-embedcollegehumor.serialized.html
index 4834b97cdea6b..71317f6a8b038 100644
--- a/blocks/test/fixtures/core-embedcollegehumor.serialized.html
+++ b/blocks/test/fixtures/core-embedcollegehumor.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedcollegehumor url="https://collegehumor.com/" -->
-<figure class="wp-block-core-embedcollegehumor">
+<figure class="wp-block-embedcollegehumor">
     https://collegehumor.com/
     <figcaption>Embedded content from collegehumor</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embeddailymotion.html b/blocks/test/fixtures/core-embeddailymotion.html
index 2eb58a3647a1b..3d5e11f2c589d 100644
--- a/blocks/test/fixtures/core-embeddailymotion.html
+++ b/blocks/test/fixtures/core-embeddailymotion.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embeddailymotion url="https://dailymotion.com/" -->
-<figure class="wp-block-core-embeddailymotion">
+<figure class="wp-block-embeddailymotion">
     https://dailymotion.com/
     <figcaption>Embedded content from dailymotion</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embeddailymotion.serialized.html b/blocks/test/fixtures/core-embeddailymotion.serialized.html
index de05b3c4e45f3..255ddf1b0dce2 100644
--- a/blocks/test/fixtures/core-embeddailymotion.serialized.html
+++ b/blocks/test/fixtures/core-embeddailymotion.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embeddailymotion url="https://dailymotion.com/" -->
-<figure class="wp-block-core-embeddailymotion">
+<figure class="wp-block-embeddailymotion">
     https://dailymotion.com/
     <figcaption>Embedded content from dailymotion</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfacebook.html b/blocks/test/fixtures/core-embedfacebook.html
index 36b195fca0219..676639abeabe7 100644
--- a/blocks/test/fixtures/core-embedfacebook.html
+++ b/blocks/test/fixtures/core-embedfacebook.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfacebook url="https://facebook.com/" -->
-<figure class="wp-block-core-embedfacebook">
+<figure class="wp-block-embedfacebook">
     https://facebook.com/
     <figcaption>Embedded content from facebook</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfacebook.serialized.html b/blocks/test/fixtures/core-embedfacebook.serialized.html
index e4e3b8cd0e2d8..32f7c6f2933c2 100644
--- a/blocks/test/fixtures/core-embedfacebook.serialized.html
+++ b/blocks/test/fixtures/core-embedfacebook.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfacebook url="https://facebook.com/" -->
-<figure class="wp-block-core-embedfacebook">
+<figure class="wp-block-embedfacebook">
     https://facebook.com/
     <figcaption>Embedded content from facebook</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedflickr.html b/blocks/test/fixtures/core-embedflickr.html
index 54eba6e3b4d9f..e3b40b68cfb11 100644
--- a/blocks/test/fixtures/core-embedflickr.html
+++ b/blocks/test/fixtures/core-embedflickr.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedflickr url="https://flickr.com/" -->
-<figure class="wp-block-core-embedflickr">
+<figure class="wp-block-embedflickr">
     https://flickr.com/
     <figcaption>Embedded content from flickr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedflickr.serialized.html b/blocks/test/fixtures/core-embedflickr.serialized.html
index 7fab45c0d0032..8253ec7d974ee 100644
--- a/blocks/test/fixtures/core-embedflickr.serialized.html
+++ b/blocks/test/fixtures/core-embedflickr.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedflickr url="https://flickr.com/" -->
-<figure class="wp-block-core-embedflickr">
+<figure class="wp-block-embedflickr">
     https://flickr.com/
     <figcaption>Embedded content from flickr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfunnyordie.html b/blocks/test/fixtures/core-embedfunnyordie.html
index 09c99b96ce3ab..d4ceb296ebeb0 100644
--- a/blocks/test/fixtures/core-embedfunnyordie.html
+++ b/blocks/test/fixtures/core-embedfunnyordie.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfunnyordie url="https://funnyordie.com/" -->
-<figure class="wp-block-core-embedfunnyordie">
+<figure class="wp-block-embedfunnyordie">
     https://funnyordie.com/
     <figcaption>Embedded content from funnyordie</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedfunnyordie.serialized.html b/blocks/test/fixtures/core-embedfunnyordie.serialized.html
index a8a9aa567f8aa..a287abe114dbc 100644
--- a/blocks/test/fixtures/core-embedfunnyordie.serialized.html
+++ b/blocks/test/fixtures/core-embedfunnyordie.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedfunnyordie url="https://funnyordie.com/" -->
-<figure class="wp-block-core-embedfunnyordie">
+<figure class="wp-block-embedfunnyordie">
     https://funnyordie.com/
     <figcaption>Embedded content from funnyordie</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedhulu.html b/blocks/test/fixtures/core-embedhulu.html
index fb19c1c5d5151..461ccafc651f9 100644
--- a/blocks/test/fixtures/core-embedhulu.html
+++ b/blocks/test/fixtures/core-embedhulu.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedhulu url="https://hulu.com/" -->
-<figure class="wp-block-core-embedhulu">
+<figure class="wp-block-embedhulu">
     https://hulu.com/
     <figcaption>Embedded content from hulu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedhulu.serialized.html b/blocks/test/fixtures/core-embedhulu.serialized.html
index 51211ebfde4a2..7bd8f13f5c54c 100644
--- a/blocks/test/fixtures/core-embedhulu.serialized.html
+++ b/blocks/test/fixtures/core-embedhulu.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedhulu url="https://hulu.com/" -->
-<figure class="wp-block-core-embedhulu">
+<figure class="wp-block-embedhulu">
     https://hulu.com/
     <figcaption>Embedded content from hulu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedimgur.html b/blocks/test/fixtures/core-embedimgur.html
index cf9ce949285e7..c99b387d89df5 100644
--- a/blocks/test/fixtures/core-embedimgur.html
+++ b/blocks/test/fixtures/core-embedimgur.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedimgur url="https://imgur.com/" -->
-<figure class="wp-block-core-embedimgur">
+<figure class="wp-block-embedimgur">
     https://imgur.com/
     <figcaption>Embedded content from imgur</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedimgur.serialized.html b/blocks/test/fixtures/core-embedimgur.serialized.html
index a22ec4622e057..6c73894b42afa 100644
--- a/blocks/test/fixtures/core-embedimgur.serialized.html
+++ b/blocks/test/fixtures/core-embedimgur.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedimgur url="https://imgur.com/" -->
-<figure class="wp-block-core-embedimgur">
+<figure class="wp-block-embedimgur">
     https://imgur.com/
     <figcaption>Embedded content from imgur</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedinstagram.html b/blocks/test/fixtures/core-embedinstagram.html
index b74d60f360a33..5532e1efac3d7 100644
--- a/blocks/test/fixtures/core-embedinstagram.html
+++ b/blocks/test/fixtures/core-embedinstagram.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedinstagram url="https://instagram.com/" -->
-<figure class="wp-block-core-embedinstagram">
+<figure class="wp-block-embedinstagram">
     https://instagram.com/
     <figcaption>Embedded content from instagram</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedinstagram.serialized.html b/blocks/test/fixtures/core-embedinstagram.serialized.html
index 789314d81df37..da883aaa69f8d 100644
--- a/blocks/test/fixtures/core-embedinstagram.serialized.html
+++ b/blocks/test/fixtures/core-embedinstagram.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedinstagram url="https://instagram.com/" -->
-<figure class="wp-block-core-embedinstagram">
+<figure class="wp-block-embedinstagram">
     https://instagram.com/
     <figcaption>Embedded content from instagram</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedissuu.html b/blocks/test/fixtures/core-embedissuu.html
index 537bed06aef59..d7b113d69ebea 100644
--- a/blocks/test/fixtures/core-embedissuu.html
+++ b/blocks/test/fixtures/core-embedissuu.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedissuu url="https://issuu.com/" -->
-<figure class="wp-block-core-embedissuu">
+<figure class="wp-block-embedissuu">
     https://issuu.com/
     <figcaption>Embedded content from issuu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedissuu.serialized.html b/blocks/test/fixtures/core-embedissuu.serialized.html
index 09fa6af235cff..523979b284dda 100644
--- a/blocks/test/fixtures/core-embedissuu.serialized.html
+++ b/blocks/test/fixtures/core-embedissuu.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedissuu url="https://issuu.com/" -->
-<figure class="wp-block-core-embedissuu">
+<figure class="wp-block-embedissuu">
     https://issuu.com/
     <figcaption>Embedded content from issuu</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedkickstarter.html b/blocks/test/fixtures/core-embedkickstarter.html
index ca7a645723b3d..9c0ab3683e23e 100644
--- a/blocks/test/fixtures/core-embedkickstarter.html
+++ b/blocks/test/fixtures/core-embedkickstarter.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedkickstarter url="https://kickstarter.com/" -->
-<figure class="wp-block-core-embedkickstarter">
+<figure class="wp-block-embedkickstarter">
     https://kickstarter.com/
     <figcaption>Embedded content from kickstarter</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedkickstarter.serialized.html b/blocks/test/fixtures/core-embedkickstarter.serialized.html
index a3820965b1c84..3cfeeaf23c71d 100644
--- a/blocks/test/fixtures/core-embedkickstarter.serialized.html
+++ b/blocks/test/fixtures/core-embedkickstarter.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedkickstarter url="https://kickstarter.com/" -->
-<figure class="wp-block-core-embedkickstarter">
+<figure class="wp-block-embedkickstarter">
     https://kickstarter.com/
     <figcaption>Embedded content from kickstarter</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmeetupcom.html b/blocks/test/fixtures/core-embedmeetupcom.html
index e70d7742dc7fb..1b85b5ec15102 100644
--- a/blocks/test/fixtures/core-embedmeetupcom.html
+++ b/blocks/test/fixtures/core-embedmeetupcom.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmeetupcom url="https://meetupcom.com/" -->
-<figure class="wp-block-core-embedmeetupcom">
+<figure class="wp-block-embedmeetupcom">
     https://meetupcom.com/
     <figcaption>Embedded content from meetupcom</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmeetupcom.serialized.html b/blocks/test/fixtures/core-embedmeetupcom.serialized.html
index 8d10823d4308c..f9482afceec40 100644
--- a/blocks/test/fixtures/core-embedmeetupcom.serialized.html
+++ b/blocks/test/fixtures/core-embedmeetupcom.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmeetupcom url="https://meetupcom.com/" -->
-<figure class="wp-block-core-embedmeetupcom">
+<figure class="wp-block-embedmeetupcom">
     https://meetupcom.com/
     <figcaption>Embedded content from meetupcom</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmixcloud.html b/blocks/test/fixtures/core-embedmixcloud.html
index 3df7723847355..694bf7d7198ae 100644
--- a/blocks/test/fixtures/core-embedmixcloud.html
+++ b/blocks/test/fixtures/core-embedmixcloud.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmixcloud url="https://mixcloud.com/" -->
-<figure class="wp-block-core-embedmixcloud">
+<figure class="wp-block-embedmixcloud">
     https://mixcloud.com/
     <figcaption>Embedded content from mixcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedmixcloud.serialized.html b/blocks/test/fixtures/core-embedmixcloud.serialized.html
index 25c977a86e271..553aaeedaf730 100644
--- a/blocks/test/fixtures/core-embedmixcloud.serialized.html
+++ b/blocks/test/fixtures/core-embedmixcloud.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedmixcloud url="https://mixcloud.com/" -->
-<figure class="wp-block-core-embedmixcloud">
+<figure class="wp-block-embedmixcloud">
     https://mixcloud.com/
     <figcaption>Embedded content from mixcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedphotobucket.html b/blocks/test/fixtures/core-embedphotobucket.html
index cd884bef1ce07..c6a485ac6697f 100644
--- a/blocks/test/fixtures/core-embedphotobucket.html
+++ b/blocks/test/fixtures/core-embedphotobucket.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedphotobucket url="https://photobucket.com/" -->
-<figure class="wp-block-core-embedphotobucket">
+<figure class="wp-block-embedphotobucket">
     https://photobucket.com/
     <figcaption>Embedded content from photobucket</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedphotobucket.serialized.html b/blocks/test/fixtures/core-embedphotobucket.serialized.html
index ddf81880fdf2e..c6ab742e7acb9 100644
--- a/blocks/test/fixtures/core-embedphotobucket.serialized.html
+++ b/blocks/test/fixtures/core-embedphotobucket.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedphotobucket url="https://photobucket.com/" -->
-<figure class="wp-block-core-embedphotobucket">
+<figure class="wp-block-embedphotobucket">
     https://photobucket.com/
     <figcaption>Embedded content from photobucket</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedpolldaddy.html b/blocks/test/fixtures/core-embedpolldaddy.html
index 508aba1c396fe..2100a77678f8b 100644
--- a/blocks/test/fixtures/core-embedpolldaddy.html
+++ b/blocks/test/fixtures/core-embedpolldaddy.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedpolldaddy url="https://polldaddy.com/" -->
-<figure class="wp-block-core-embedpolldaddy">
+<figure class="wp-block-embedpolldaddy">
     https://polldaddy.com/
     <figcaption>Embedded content from polldaddy</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedpolldaddy.serialized.html b/blocks/test/fixtures/core-embedpolldaddy.serialized.html
index 4d8cbb5f91af0..eb03ce80833c7 100644
--- a/blocks/test/fixtures/core-embedpolldaddy.serialized.html
+++ b/blocks/test/fixtures/core-embedpolldaddy.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedpolldaddy url="https://polldaddy.com/" -->
-<figure class="wp-block-core-embedpolldaddy">
+<figure class="wp-block-embedpolldaddy">
     https://polldaddy.com/
     <figcaption>Embedded content from polldaddy</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreddit.html b/blocks/test/fixtures/core-embedreddit.html
index 2b083415c3b61..e65afcbd57a50 100644
--- a/blocks/test/fixtures/core-embedreddit.html
+++ b/blocks/test/fixtures/core-embedreddit.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreddit url="https://reddit.com/" -->
-<figure class="wp-block-core-embedreddit">
+<figure class="wp-block-embedreddit">
     https://reddit.com/
     <figcaption>Embedded content from reddit</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreddit.serialized.html b/blocks/test/fixtures/core-embedreddit.serialized.html
index ec9e894c51185..132abb68d19bf 100644
--- a/blocks/test/fixtures/core-embedreddit.serialized.html
+++ b/blocks/test/fixtures/core-embedreddit.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreddit url="https://reddit.com/" -->
-<figure class="wp-block-core-embedreddit">
+<figure class="wp-block-embedreddit">
     https://reddit.com/
     <figcaption>Embedded content from reddit</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreverbnation.html b/blocks/test/fixtures/core-embedreverbnation.html
index 36923f77f1035..5cbaf057fc287 100644
--- a/blocks/test/fixtures/core-embedreverbnation.html
+++ b/blocks/test/fixtures/core-embedreverbnation.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreverbnation url="https://reverbnation.com/" -->
-<figure class="wp-block-core-embedreverbnation">
+<figure class="wp-block-embedreverbnation">
     https://reverbnation.com/
     <figcaption>Embedded content from reverbnation</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedreverbnation.serialized.html b/blocks/test/fixtures/core-embedreverbnation.serialized.html
index 7482ef1e1604b..423d043a84844 100644
--- a/blocks/test/fixtures/core-embedreverbnation.serialized.html
+++ b/blocks/test/fixtures/core-embedreverbnation.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedreverbnation url="https://reverbnation.com/" -->
-<figure class="wp-block-core-embedreverbnation">
+<figure class="wp-block-embedreverbnation">
     https://reverbnation.com/
     <figcaption>Embedded content from reverbnation</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscreencast.html b/blocks/test/fixtures/core-embedscreencast.html
index 5f7a10844a7ce..13a6bfc932442 100644
--- a/blocks/test/fixtures/core-embedscreencast.html
+++ b/blocks/test/fixtures/core-embedscreencast.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscreencast url="https://screencast.com/" -->
-<figure class="wp-block-core-embedscreencast">
+<figure class="wp-block-embedscreencast">
     https://screencast.com/
     <figcaption>Embedded content from screencast</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscreencast.serialized.html b/blocks/test/fixtures/core-embedscreencast.serialized.html
index efea68a484219..531f502cbf2d2 100644
--- a/blocks/test/fixtures/core-embedscreencast.serialized.html
+++ b/blocks/test/fixtures/core-embedscreencast.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscreencast url="https://screencast.com/" -->
-<figure class="wp-block-core-embedscreencast">
+<figure class="wp-block-embedscreencast">
     https://screencast.com/
     <figcaption>Embedded content from screencast</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscribd.html b/blocks/test/fixtures/core-embedscribd.html
index a4872f0920b6b..c1fa083daa8b7 100644
--- a/blocks/test/fixtures/core-embedscribd.html
+++ b/blocks/test/fixtures/core-embedscribd.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscribd url="https://scribd.com/" -->
-<figure class="wp-block-core-embedscribd">
+<figure class="wp-block-embedscribd">
     https://scribd.com/
     <figcaption>Embedded content from scribd</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedscribd.serialized.html b/blocks/test/fixtures/core-embedscribd.serialized.html
index d1a1fb5e94167..297a990fbfc76 100644
--- a/blocks/test/fixtures/core-embedscribd.serialized.html
+++ b/blocks/test/fixtures/core-embedscribd.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedscribd url="https://scribd.com/" -->
-<figure class="wp-block-core-embedscribd">
+<figure class="wp-block-embedscribd">
     https://scribd.com/
     <figcaption>Embedded content from scribd</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedslideshare.html b/blocks/test/fixtures/core-embedslideshare.html
index ae29ae9b10857..22122bfbc7fbc 100644
--- a/blocks/test/fixtures/core-embedslideshare.html
+++ b/blocks/test/fixtures/core-embedslideshare.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedslideshare url="https://slideshare.com/" -->
-<figure class="wp-block-core-embedslideshare">
+<figure class="wp-block-embedslideshare">
     https://slideshare.com/
     <figcaption>Embedded content from slideshare</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedslideshare.serialized.html b/blocks/test/fixtures/core-embedslideshare.serialized.html
index 89ad51a722de8..b36aa00eae92e 100644
--- a/blocks/test/fixtures/core-embedslideshare.serialized.html
+++ b/blocks/test/fixtures/core-embedslideshare.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedslideshare url="https://slideshare.com/" -->
-<figure class="wp-block-core-embedslideshare">
+<figure class="wp-block-embedslideshare">
     https://slideshare.com/
     <figcaption>Embedded content from slideshare</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsmugmug.html b/blocks/test/fixtures/core-embedsmugmug.html
index a778508749c0a..051ac4f2a5dfe 100644
--- a/blocks/test/fixtures/core-embedsmugmug.html
+++ b/blocks/test/fixtures/core-embedsmugmug.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsmugmug url="https://smugmug.com/" -->
-<figure class="wp-block-core-embedsmugmug">
+<figure class="wp-block-embedsmugmug">
     https://smugmug.com/
     <figcaption>Embedded content from smugmug</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsmugmug.serialized.html b/blocks/test/fixtures/core-embedsmugmug.serialized.html
index ae83583b91075..861ea30e9cd8a 100644
--- a/blocks/test/fixtures/core-embedsmugmug.serialized.html
+++ b/blocks/test/fixtures/core-embedsmugmug.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsmugmug url="https://smugmug.com/" -->
-<figure class="wp-block-core-embedsmugmug">
+<figure class="wp-block-embedsmugmug">
     https://smugmug.com/
     <figcaption>Embedded content from smugmug</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsoundcloud.html b/blocks/test/fixtures/core-embedsoundcloud.html
index 3bc156f303e82..71861f3fc70f3 100644
--- a/blocks/test/fixtures/core-embedsoundcloud.html
+++ b/blocks/test/fixtures/core-embedsoundcloud.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsoundcloud url="https://soundcloud.com/" -->
-<figure class="wp-block-core-embedsoundcloud">
+<figure class="wp-block-embedsoundcloud">
     https://soundcloud.com/
     <figcaption>Embedded content from soundcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedsoundcloud.serialized.html b/blocks/test/fixtures/core-embedsoundcloud.serialized.html
index 0edbe298420f7..737adfdf9783e 100644
--- a/blocks/test/fixtures/core-embedsoundcloud.serialized.html
+++ b/blocks/test/fixtures/core-embedsoundcloud.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedsoundcloud url="https://soundcloud.com/" -->
-<figure class="wp-block-core-embedsoundcloud">
+<figure class="wp-block-embedsoundcloud">
     https://soundcloud.com/
     <figcaption>Embedded content from soundcloud</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspeaker.html b/blocks/test/fixtures/core-embedspeaker.html
index 77aec2c0c2d99..b867ca3306628 100644
--- a/blocks/test/fixtures/core-embedspeaker.html
+++ b/blocks/test/fixtures/core-embedspeaker.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspeaker url="https://speaker.com/" -->
-<figure class="wp-block-core-embedspeaker">
+<figure class="wp-block-embedspeaker">
     https://speaker.com/
     <figcaption>Embedded content from speaker</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspeaker.serialized.html b/blocks/test/fixtures/core-embedspeaker.serialized.html
index 5c880c62d7589..6ff3f887897f4 100644
--- a/blocks/test/fixtures/core-embedspeaker.serialized.html
+++ b/blocks/test/fixtures/core-embedspeaker.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspeaker url="https://speaker.com/" -->
-<figure class="wp-block-core-embedspeaker">
+<figure class="wp-block-embedspeaker">
     https://speaker.com/
     <figcaption>Embedded content from speaker</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspotify.html b/blocks/test/fixtures/core-embedspotify.html
index cae29199f19c1..c7d30a15cce87 100644
--- a/blocks/test/fixtures/core-embedspotify.html
+++ b/blocks/test/fixtures/core-embedspotify.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspotify url="https://spotify.com/" -->
-<figure class="wp-block-core-embedspotify">
+<figure class="wp-block-embedspotify">
     https://spotify.com/
     <figcaption>Embedded content from spotify</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedspotify.serialized.html b/blocks/test/fixtures/core-embedspotify.serialized.html
index 13ca4f3798771..76758f39e77f8 100644
--- a/blocks/test/fixtures/core-embedspotify.serialized.html
+++ b/blocks/test/fixtures/core-embedspotify.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedspotify url="https://spotify.com/" -->
-<figure class="wp-block-core-embedspotify">
+<figure class="wp-block-embedspotify">
     https://spotify.com/
     <figcaption>Embedded content from spotify</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedted.html b/blocks/test/fixtures/core-embedted.html
index 2546b6d74bd31..d2f5b32252003 100644
--- a/blocks/test/fixtures/core-embedted.html
+++ b/blocks/test/fixtures/core-embedted.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedted url="https://ted.com/" -->
-<figure class="wp-block-core-embedted">
+<figure class="wp-block-embedted">
     https://ted.com/
     <figcaption>Embedded content from ted</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedted.serialized.html b/blocks/test/fixtures/core-embedted.serialized.html
index 638848a4cada2..d31e228747781 100644
--- a/blocks/test/fixtures/core-embedted.serialized.html
+++ b/blocks/test/fixtures/core-embedted.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedted url="https://ted.com/" -->
-<figure class="wp-block-core-embedted">
+<figure class="wp-block-embedted">
     https://ted.com/
     <figcaption>Embedded content from ted</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtumblr.html b/blocks/test/fixtures/core-embedtumblr.html
index 0a1fc1a1292bb..5b61b112a44e4 100644
--- a/blocks/test/fixtures/core-embedtumblr.html
+++ b/blocks/test/fixtures/core-embedtumblr.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtumblr url="https://tumblr.com/" -->
-<figure class="wp-block-core-embedtumblr">
+<figure class="wp-block-embedtumblr">
     https://tumblr.com/
     <figcaption>Embedded content from tumblr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtumblr.serialized.html b/blocks/test/fixtures/core-embedtumblr.serialized.html
index b31aa5ad8714b..2143be60542c5 100644
--- a/blocks/test/fixtures/core-embedtumblr.serialized.html
+++ b/blocks/test/fixtures/core-embedtumblr.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtumblr url="https://tumblr.com/" -->
-<figure class="wp-block-core-embedtumblr">
+<figure class="wp-block-embedtumblr">
     https://tumblr.com/
     <figcaption>Embedded content from tumblr</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtwitter.html b/blocks/test/fixtures/core-embedtwitter.html
index 14604151a39ea..b72be15a1f079 100644
--- a/blocks/test/fixtures/core-embedtwitter.html
+++ b/blocks/test/fixtures/core-embedtwitter.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtwitter url="https://twitter.com/automattic" -->
-<figure class="wp-block-core-embedtwitter">
+<figure class="wp-block-embedtwitter">
     https://twitter.com/automattic
     <figcaption>We are Automattic</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedtwitter.serialized.html b/blocks/test/fixtures/core-embedtwitter.serialized.html
index d959f9f76912b..ae9ec684986a5 100644
--- a/blocks/test/fixtures/core-embedtwitter.serialized.html
+++ b/blocks/test/fixtures/core-embedtwitter.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedtwitter url="https://twitter.com/automattic" -->
-<figure class="wp-block-core-embedtwitter">
+<figure class="wp-block-embedtwitter">
     https://twitter.com/automattic
     <figcaption>We are Automattic</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvideopress.html b/blocks/test/fixtures/core-embedvideopress.html
index 852ca78e203f0..3169a6c898123 100644
--- a/blocks/test/fixtures/core-embedvideopress.html
+++ b/blocks/test/fixtures/core-embedvideopress.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvideopress url="https://videopress.com/" -->
-<figure class="wp-block-core-embedvideopress">
+<figure class="wp-block-embedvideopress">
     https://videopress.com/
     <figcaption>Embedded content from videopress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvideopress.serialized.html b/blocks/test/fixtures/core-embedvideopress.serialized.html
index 5ad3deaeae761..f7f47f95158b0 100644
--- a/blocks/test/fixtures/core-embedvideopress.serialized.html
+++ b/blocks/test/fixtures/core-embedvideopress.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvideopress url="https://videopress.com/" -->
-<figure class="wp-block-core-embedvideopress">
+<figure class="wp-block-embedvideopress">
     https://videopress.com/
     <figcaption>Embedded content from videopress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvimeo.html b/blocks/test/fixtures/core-embedvimeo.html
index 3e3ecf54288a9..19a10852c9e5f 100644
--- a/blocks/test/fixtures/core-embedvimeo.html
+++ b/blocks/test/fixtures/core-embedvimeo.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvimeo url="https://vimeo.com/" -->
-<figure class="wp-block-core-embedvimeo">
+<figure class="wp-block-embedvimeo">
     https://vimeo.com/
     <figcaption>Embedded content from vimeo</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvimeo.serialized.html b/blocks/test/fixtures/core-embedvimeo.serialized.html
index c23c39d52ad4f..d822d6ea7842a 100644
--- a/blocks/test/fixtures/core-embedvimeo.serialized.html
+++ b/blocks/test/fixtures/core-embedvimeo.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvimeo url="https://vimeo.com/" -->
-<figure class="wp-block-core-embedvimeo">
+<figure class="wp-block-embedvimeo">
     https://vimeo.com/
     <figcaption>Embedded content from vimeo</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvine.html b/blocks/test/fixtures/core-embedvine.html
index e7ed0d2f98847..cc59f6594119e 100644
--- a/blocks/test/fixtures/core-embedvine.html
+++ b/blocks/test/fixtures/core-embedvine.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvine url="https://vine.com/" -->
-<figure class="wp-block-core-embedvine">
+<figure class="wp-block-embedvine">
     https://vine.com/
     <figcaption>Embedded content from vine</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedvine.serialized.html b/blocks/test/fixtures/core-embedvine.serialized.html
index 23877d1ece71c..5f16f77d73f44 100644
--- a/blocks/test/fixtures/core-embedvine.serialized.html
+++ b/blocks/test/fixtures/core-embedvine.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedvine url="https://vine.com/" -->
-<figure class="wp-block-core-embedvine">
+<figure class="wp-block-embedvine">
     https://vine.com/
     <figcaption>Embedded content from vine</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpress.html b/blocks/test/fixtures/core-embedwordpress.html
index e16386905c58a..2d33a2f8bca5c 100644
--- a/blocks/test/fixtures/core-embedwordpress.html
+++ b/blocks/test/fixtures/core-embedwordpress.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpress url="https://wordpress.com/" -->
-<figure class="wp-block-core-embedwordpress">
+<figure class="wp-block-embedwordpress">
     https://wordpress.com/
     <figcaption>Embedded content from WordPress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpress.serialized.html b/blocks/test/fixtures/core-embedwordpress.serialized.html
index 9748cc91b9e3b..6fb0d81613dfe 100644
--- a/blocks/test/fixtures/core-embedwordpress.serialized.html
+++ b/blocks/test/fixtures/core-embedwordpress.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpress url="https://wordpress.com/" -->
-<figure class="wp-block-core-embedwordpress">
+<figure class="wp-block-embedwordpress">
     https://wordpress.com/
     <figcaption>Embedded content from WordPress</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpresstv.html b/blocks/test/fixtures/core-embedwordpresstv.html
index 3675fe56b6f5d..f2639556cca0f 100644
--- a/blocks/test/fixtures/core-embedwordpresstv.html
+++ b/blocks/test/fixtures/core-embedwordpresstv.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpresstv url="https://wordpresstv.com/" -->
-<figure class="wp-block-core-embedwordpresstv">
+<figure class="wp-block-embedwordpresstv">
     https://wordpresstv.com/
     <figcaption>Embedded content from wordpresstv</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedwordpresstv.serialized.html b/blocks/test/fixtures/core-embedwordpresstv.serialized.html
index a906d563357c0..ce9ce84fc9a26 100644
--- a/blocks/test/fixtures/core-embedwordpresstv.serialized.html
+++ b/blocks/test/fixtures/core-embedwordpresstv.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedwordpresstv url="https://wordpresstv.com/" -->
-<figure class="wp-block-core-embedwordpresstv">
+<figure class="wp-block-embedwordpresstv">
     https://wordpresstv.com/
     <figcaption>Embedded content from wordpresstv</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedyoutube.html b/blocks/test/fixtures/core-embedyoutube.html
index b97d4fa9c7a34..026763327b62a 100644
--- a/blocks/test/fixtures/core-embedyoutube.html
+++ b/blocks/test/fixtures/core-embedyoutube.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedyoutube url="https://youtube.com/" -->
-<figure class="wp-block-core-embedyoutube">
+<figure class="wp-block-embedyoutube">
     https://youtube.com/
     <figcaption>Embedded content from youtube</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-embedyoutube.serialized.html b/blocks/test/fixtures/core-embedyoutube.serialized.html
index f5ed0ba74ddf9..8c1a1265bf504 100644
--- a/blocks/test/fixtures/core-embedyoutube.serialized.html
+++ b/blocks/test/fixtures/core-embedyoutube.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/embedyoutube url="https://youtube.com/" -->
-<figure class="wp-block-core-embedyoutube">
+<figure class="wp-block-embedyoutube">
     https://youtube.com/
     <figcaption>Embedded content from youtube</figcaption>
 </figure>
diff --git a/blocks/test/fixtures/core-freeform.serialized.html b/blocks/test/fixtures/core-freeform.serialized.html
index e603f3513a0dd..a31ee92b0385e 100644
--- a/blocks/test/fixtures/core-freeform.serialized.html
+++ b/blocks/test/fixtures/core-freeform.serialized.html
@@ -1,6 +1,6 @@
 <!-- wp:core/freeform -->
 Testing freeform block with some
-<div class="wp-some-class wp-block-core-freeform">
+<div class="wp-some-class wp-block-freeform">
     HTML <span style="color:red;">content</span>
 </div>
 <!-- /wp:core/freeform -->
diff --git a/blocks/test/fixtures/core-gallery.html b/blocks/test/fixtures/core-gallery.html
index d313804cbb125..f60cc60da9abe 100644
--- a/blocks/test/fixtures/core-gallery.html
+++ b/blocks/test/fixtures/core-gallery.html
@@ -1,5 +1,5 @@
 <!-- wp:core/gallery -->
-<div class="blocks-gallery wp-block-core-gallery">
+<div class="blocks-gallery wp-block-gallery">
 	<figure class="blocks-gallery-image">
 		<img src="https://cldup.com/uuUqE_dXzy.jpg" alt="title" />
 	</figure>
diff --git a/blocks/test/fixtures/core-gallery.serialized.html b/blocks/test/fixtures/core-gallery.serialized.html
index eaf79d8e492be..4295680cc60b1 100644
--- a/blocks/test/fixtures/core-gallery.serialized.html
+++ b/blocks/test/fixtures/core-gallery.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/gallery -->
-<div class="blocks-gallery alignnone columns-2 wp-block-core-gallery">
+<div class="blocks-gallery alignnone columns-2 wp-block-gallery">
     <figure class="blocks-gallery-image"><img src="https://cldup.com/uuUqE_dXzy.jpg" alt="title" /></figure>
     <figure class="blocks-gallery-image"><img src="http://google.com/hi.png" alt="title" /></figure>
 </div>
diff --git a/blocks/test/fixtures/core-heading-h2-em.html b/blocks/test/fixtures/core-heading-h2-em.html
index 38394de2ad218..b301eb4fbfae0 100644
--- a/blocks/test/fixtures/core-heading-h2-em.html
+++ b/blocks/test/fixtures/core-heading-h2-em.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-core-heading">The <em>Inserter</em> Tool</h2>
+<h2 class="wp-block-heading">The <em>Inserter</em> Tool</h2>
 <!-- /wp:core/heading -->
diff --git a/blocks/test/fixtures/core-heading-h2-em.serialized.html b/blocks/test/fixtures/core-heading-h2-em.serialized.html
index d8f0267a69ab5..7fc5a6497df1c 100644
--- a/blocks/test/fixtures/core-heading-h2-em.serialized.html
+++ b/blocks/test/fixtures/core-heading-h2-em.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-core-heading">The <em>Inserter</em> Tool</h2>
+<h2 class="wp-block-heading">The <em>Inserter</em> Tool</h2>
 <!-- /wp:core/heading -->
 
diff --git a/blocks/test/fixtures/core-heading-h2.html b/blocks/test/fixtures/core-heading-h2.html
index c9baba90b8186..d7b487af0b670 100644
--- a/blocks/test/fixtures/core-heading-h2.html
+++ b/blocks/test/fixtures/core-heading-h2.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-core-heading">A picture is worth a thousand words, or so the saying goes</h2>
+<h2 class="wp-block-heading">A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:core/heading -->
diff --git a/blocks/test/fixtures/core-heading-h2.serialized.html b/blocks/test/fixtures/core-heading-h2.serialized.html
index db488794ad4f2..437f79dbb01ce 100644
--- a/blocks/test/fixtures/core-heading-h2.serialized.html
+++ b/blocks/test/fixtures/core-heading-h2.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-core-heading">A picture is worth a thousand words, or so the saying goes</h2>
+<h2 class="wp-block-heading">A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:core/heading -->
 
diff --git a/blocks/test/fixtures/core-image-center-caption.html b/blocks/test/fixtures/core-image-center-caption.html
index 5a4b63a0b35a6..0aa89dced8561 100644
--- a/blocks/test/fixtures/core-image-center-caption.html
+++ b/blocks/test/fixtures/core-image-center-caption.html
@@ -1,3 +1,3 @@
 <!-- wp:core/image align="center" -->
-<figure class="wp-block-core-image"><img src="https://cldup.com/YLYhpou2oq.jpg" class="aligncenter"/><figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption></figure>
+<figure class="wp-block-image"><img src="https://cldup.com/YLYhpou2oq.jpg" class="aligncenter"/><figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption></figure>
 <!-- /wp:core/image -->
diff --git a/blocks/test/fixtures/core-image-center-caption.serialized.html b/blocks/test/fixtures/core-image-center-caption.serialized.html
index db8452ea131fc..b2e649e4018c4 100644
--- a/blocks/test/fixtures/core-image-center-caption.serialized.html
+++ b/blocks/test/fixtures/core-image-center-caption.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/image align="center" -->
-<figure class="aligncenter wp-block-core-image"><img src="https://cldup.com/YLYhpou2oq.jpg" />
+<figure class="aligncenter wp-block-image"><img src="https://cldup.com/YLYhpou2oq.jpg" />
     <figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption>
 </figure>
 <!-- /wp:core/image -->
diff --git a/blocks/test/fixtures/core-image.html b/blocks/test/fixtures/core-image.html
index 42bdd73fca695..2a414855b0344 100644
--- a/blocks/test/fixtures/core-image.html
+++ b/blocks/test/fixtures/core-image.html
@@ -1,3 +1,3 @@
 <!-- wp:core/image -->
-<figure class="wp-block-core-image"><img src="https://cldup.com/uuUqE_dXzy.jpg" /></figure>
+<figure class="wp-block-image"><img src="https://cldup.com/uuUqE_dXzy.jpg" /></figure>
 <!-- /wp:core/image -->
diff --git a/blocks/test/fixtures/core-image.serialized.html b/blocks/test/fixtures/core-image.serialized.html
index d4050b47a8121..103b958254279 100644
--- a/blocks/test/fixtures/core-image.serialized.html
+++ b/blocks/test/fixtures/core-image.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/image -->
-<img src="https://cldup.com/uuUqE_dXzy.jpg" class="alignnone wp-block-core-image" />
+<img src="https://cldup.com/uuUqE_dXzy.jpg" class="alignnone wp-block-image" />
 <!-- /wp:core/image -->
 
diff --git a/blocks/test/fixtures/core-list-ul.html b/blocks/test/fixtures/core-list-ul.html
index 1af7352863290..565bbe3c19c77 100644
--- a/blocks/test/fixtures/core-list-ul.html
+++ b/blocks/test/fixtures/core-list-ul.html
@@ -1,3 +1,3 @@
 <!-- wp:core/list -->
-<ul class="wp-block-core-list"><li>Text & Headings</li><li>Images & Videos</li><li>Galleries</li><li>Embeds, like YouTube, Tweets, or other WordPress posts.</li><li>Layout blocks, like Buttons, Hero Images, Separators, etc.</li><li>And <em>Lists</em> like this one of course :)</li></ul>
+<ul class="wp-block-list"><li>Text & Headings</li><li>Images & Videos</li><li>Galleries</li><li>Embeds, like YouTube, Tweets, or other WordPress posts.</li><li>Layout blocks, like Buttons, Hero Images, Separators, etc.</li><li>And <em>Lists</em> like this one of course :)</li></ul>
 <!-- /wp:core/list -->
diff --git a/blocks/test/fixtures/core-list-ul.serialized.html b/blocks/test/fixtures/core-list-ul.serialized.html
index 8386d37b0ad9a..1496949eb48f1 100644
--- a/blocks/test/fixtures/core-list-ul.serialized.html
+++ b/blocks/test/fixtures/core-list-ul.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/list -->
-<ul class="wp-block-core-list">
+<ul class="wp-block-list">
     <li>Text &amp; Headings</li>
     <li>Images &amp; Videos</li>
     <li>Galleries</li>
diff --git a/blocks/test/fixtures/core-preformatted.html b/blocks/test/fixtures/core-preformatted.html
index 820c5eed8a096..1a890a7a5dc2d 100644
--- a/blocks/test/fixtures/core-preformatted.html
+++ b/blocks/test/fixtures/core-preformatted.html
@@ -1,3 +1,3 @@
 <!-- wp:core/preformatted -->
-<pre class="wp-block-core-preformatted">Some <em>preformatted</em> text...<br>And more!</pre>
+<pre class="wp-block-preformatted">Some <em>preformatted</em> text...<br>And more!</pre>
 <!-- /wp:core/preformatted -->
diff --git a/blocks/test/fixtures/core-preformatted.serialized.html b/blocks/test/fixtures/core-preformatted.serialized.html
index cf82d1da30d94..ae726c700d0f1 100644
--- a/blocks/test/fixtures/core-preformatted.serialized.html
+++ b/blocks/test/fixtures/core-preformatted.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/preformatted -->
-<pre class="wp-block-core-preformatted">Some <em>preformatted</em> text...<br/>And more!</pre>
+<pre class="wp-block-preformatted">Some <em>preformatted</em> text...<br/>And more!</pre>
 <!-- /wp:core/preformatted -->
 
diff --git a/blocks/test/fixtures/core-pullquote.html b/blocks/test/fixtures/core-pullquote.html
index 8bb7a431b413a..2fa9569cddae2 100644
--- a/blocks/test/fixtures/core-pullquote.html
+++ b/blocks/test/fixtures/core-pullquote.html
@@ -1,5 +1,5 @@
 <!-- wp:core/pullquote -->
-<blockquote class="blocks-pullquote wp-block-core-pullquote">
+<blockquote class="blocks-pullquote wp-block-pullquote">
 <p>Testing pullquote block...</p><footer>...with a caption</footer>
 </blockquote>
 <!-- /wp:core/pullquote -->
diff --git a/blocks/test/fixtures/core-pullquote.serialized.html b/blocks/test/fixtures/core-pullquote.serialized.html
index 81f69727fac92..dc34d4f9689f9 100644
--- a/blocks/test/fixtures/core-pullquote.serialized.html
+++ b/blocks/test/fixtures/core-pullquote.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/pullquote -->
-<blockquote class="blocks-pullquote alignnone wp-block-core-pullquote">
+<blockquote class="blocks-pullquote alignnone wp-block-pullquote">
     <p>Testing pullquote block...</p>
     <footer>...with a caption</footer>
 </blockquote>
diff --git a/blocks/test/fixtures/core-quote-style-1.html b/blocks/test/fixtures/core-quote-style-1.html
index 5a57c31317c84..a78cd61bba985 100644
--- a/blocks/test/fixtures/core-quote-style-1.html
+++ b/blocks/test/fixtures/core-quote-style-1.html
@@ -1,3 +1,3 @@
 <!-- wp:core/quote style="1" -->
-<blockquote class="blocks-quote-style-1 wp-block-core-quote"><p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p><footer>Matt Mullenweg, 2017</footer></blockquote>
+<blockquote class="blocks-quote-style-1 wp-block-quote"><p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p><footer>Matt Mullenweg, 2017</footer></blockquote>
 <!-- /wp:core/quote -->
diff --git a/blocks/test/fixtures/core-quote-style-1.serialized.html b/blocks/test/fixtures/core-quote-style-1.serialized.html
index cc81c868f7bcd..b89cf527cb38c 100644
--- a/blocks/test/fixtures/core-quote-style-1.serialized.html
+++ b/blocks/test/fixtures/core-quote-style-1.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/quote style="1" -->
-<blockquote class="blocks-quote-style-1 wp-block-core-quote">
+<blockquote class="blocks-quote-style-1 wp-block-quote">
     <p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p>
     <footer>Matt Mullenweg, 2017</footer>
 </blockquote>
diff --git a/blocks/test/fixtures/core-quote-style-2.html b/blocks/test/fixtures/core-quote-style-2.html
index 09f9416597e4f..5770cb815e678 100644
--- a/blocks/test/fixtures/core-quote-style-2.html
+++ b/blocks/test/fixtures/core-quote-style-2.html
@@ -1,3 +1,3 @@
 <!-- wp:core/quote style="2" -->
-<blockquote class="blocks-quote-style-2 wp-block-core-quote"><p>There is no greater agony than bearing an untold story inside you.</p><footer>Maya Angelou</footer></blockquote>
+<blockquote class="blocks-quote-style-2 wp-block-quote"><p>There is no greater agony than bearing an untold story inside you.</p><footer>Maya Angelou</footer></blockquote>
 <!-- /wp:core/quote -->
diff --git a/blocks/test/fixtures/core-quote-style-2.serialized.html b/blocks/test/fixtures/core-quote-style-2.serialized.html
index 7a0c8090065be..94750496b9a4f 100644
--- a/blocks/test/fixtures/core-quote-style-2.serialized.html
+++ b/blocks/test/fixtures/core-quote-style-2.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/quote style="2" -->
-<blockquote class="blocks-quote-style-2 wp-block-core-quote">
+<blockquote class="blocks-quote-style-2 wp-block-quote">
     <p>There is no greater agony than bearing an untold story inside you.</p>
     <footer>Maya Angelou</footer>
 </blockquote>
diff --git a/blocks/test/fixtures/core-separator.html b/blocks/test/fixtures/core-separator.html
index e3e01dd1d028e..d835a483147f1 100644
--- a/blocks/test/fixtures/core-separator.html
+++ b/blocks/test/fixtures/core-separator.html
@@ -1,3 +1,3 @@
 <!-- wp:core/separator -->
-<hr class="wp-block-core-separator" />
+<hr class="wp-block-separator" />
 <!-- /wp:core/separator -->
diff --git a/blocks/test/fixtures/core-separator.serialized.html b/blocks/test/fixtures/core-separator.serialized.html
index 322c9b6a52f30..0cc337d26dc88 100644
--- a/blocks/test/fixtures/core-separator.serialized.html
+++ b/blocks/test/fixtures/core-separator.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/separator -->
-<hr class="wp-block-core-separator" />
+<hr class="wp-block-separator" />
 <!-- /wp:core/separator -->
 
diff --git a/blocks/test/fixtures/core-table.html b/blocks/test/fixtures/core-table.html
index dea1f2fe34ef0..de0498f605be4 100644
--- a/blocks/test/fixtures/core-table.html
+++ b/blocks/test/fixtures/core-table.html
@@ -1,5 +1,5 @@
 <!-- wp:core/table -->
-<table class="wp-block-core-table">
+<table class="wp-block-table">
     <thead>
         <tr>
             <th>Version</th>
diff --git a/blocks/test/fixtures/core-table.serialized.html b/blocks/test/fixtures/core-table.serialized.html
index 45e1d6995bb6a..40d9109b06271 100644
--- a/blocks/test/fixtures/core-table.serialized.html
+++ b/blocks/test/fixtures/core-table.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/table -->
-<table class="wp-block-core-table">
+<table class="wp-block-table">
     <thead>
         <tr>
             <th>Version</th>
diff --git a/blocks/test/fixtures/core-text-align-right.html b/blocks/test/fixtures/core-text-align-right.html
index 878426843f9e1..84087f8d69135 100644
--- a/blocks/test/fixtures/core-text-align-right.html
+++ b/blocks/test/fixtures/core-text-align-right.html
@@ -1,3 +1,3 @@
 <!-- wp:core/text align="right" -->
-<p class="wp-block-core-text" style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
+<p class="wp-block-text" style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
 <!-- /wp:core/text -->
diff --git a/blocks/test/fixtures/core-text-align-right.serialized.html b/blocks/test/fixtures/core-text-align-right.serialized.html
index 08cbf1aa903d8..e144eab376ffa 100644
--- a/blocks/test/fixtures/core-text-align-right.serialized.html
+++ b/blocks/test/fixtures/core-text-align-right.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/text align="right" -->
-<p style="text-align:right;" class="wp-block-core-text">... like this one, which is separate from the above and right aligned.</p>
+<p style="text-align:right;" class="wp-block-text">... like this one, which is separate from the above and right aligned.</p>
 <!-- /wp:core/text -->
 

From a057ec1e237553bca5902e2b099ae15bfb25b03f Mon Sep 17 00:00:00 2001
From: Riad Benguella <benguella@gmail.com>
Date: Fri, 23 Jun 2017 15:17:00 +0100
Subject: [PATCH 3/7] Blocks: Allowing to override the default classname
 generated for a block

---
 blocks/api/serializer.js                      | 34 +++++++----
 blocks/api/test/serializer.js                 | 56 +++++++++++++++----
 blocks/library/heading/index.js               |  2 +
 blocks/library/text/index.js                  |  2 +
 blocks/test/fixtures/core-heading-h2-em.html  |  2 +-
 .../core-heading-h2-em.serialized.html        |  2 +-
 blocks/test/fixtures/core-heading-h2.html     |  2 +-
 .../fixtures/core-heading-h2.serialized.html  |  2 +-
 .../test/fixtures/core-text-align-right.html  |  2 +-
 .../core-text-align-right.serialized.html     |  2 +-
 10 files changed, 77 insertions(+), 29 deletions(-)

diff --git a/blocks/api/serializer.js b/blocks/api/serializer.js
index 53cd689e10cc9..78b93d29535db 100644
--- a/blocks/api/serializer.js
+++ b/blocks/api/serializer.js
@@ -17,15 +17,29 @@ import { getBlockType } from './registration';
 import { parseBlockAttributes } from './parser';
 
 /**
- * Given a block's save render implementation and attributes, returns the
+ * Returns the block's default classname from its name
+ *
+ * @param {String}   blockName  The block name
+ * @return {string}             The block's default class
+ */
+export function getBlockDefaultClassname( blockName ) {
+	// Drop the namespace "core/"" for core blocks only
+	const match = /^([a-z0-9-]+)\/([a-z0-9-]+)$/.exec( blockName );
+	const sanitizedBlockName = match[ 1 ] === 'core' ? match[ 2 ] : blockName;
+
+	return `wp-block-${ kebabCase( sanitizedBlockName ) }`;
+}
+
+/**
+ * Given a block type containg a save render implementation and attributes, returns the
  * static markup to be saved.
  *
- * @param  {Function|WPComponent} save       Save render implementation
- * @param  {String}               blockName  Block name
+ * @param  {Object}               blockType  Block type
  * @param  {Object}               attributes Block attributes
  * @return {string}                          Save content
  */
-export function getSaveContent( save, blockName, attributes ) {
+export function getSaveContent( blockType, attributes ) {
+	const { save, className = getBlockDefaultClassname( blockType.name ) } = blockType;
 	let rawContent;
 
 	if ( save.prototype instanceof Component ) {
@@ -41,16 +55,12 @@ export function getSaveContent( save, blockName, attributes ) {
 
 	// Adding a generic classname
 	const addClassnameToElement = ( element ) => {
-		if ( ! element || ! isObject( element ) ) {
+		if ( ! element || ! isObject( element ) || ! className ) {
 			return element;
 		}
 
-		// Drop the namespace "core/"" for core blocks only
-		const match = /^([a-z0-9-]+)\/([a-z0-9-]+)$/.exec( blockName );
-		const sanitizedBlockName = match[ 1 ] === 'core' ? match[ 2 ] : blockName;
-
-		const className = classnames( element.props.className, `wp-block-${ kebabCase( sanitizedBlockName ) }` );
-		return cloneElement( element, { className } );
+		const updatedClassName = classnames( element.props.className, className );
+		return cloneElement( element, { className: updatedClassName } );
 	};
 	const contentWithClassname = Children.map( rawContent, addClassnameToElement );
 
@@ -124,7 +134,7 @@ function asNameValuePair( value, key ) {
 export function serializeBlock( block ) {
 	const blockName = block.name;
 	const blockType = getBlockType( blockName );
-	const saveContent = getSaveContent( blockType.save, blockName, block.attributes );
+	const saveContent = getSaveContent( blockType, block.attributes );
 	const saveAttributes = getCommentAttributes( block.attributes, parseBlockAttributes( saveContent, blockType ) );
 
 	const serializedAttributes = ! isEmpty( saveAttributes )
diff --git a/blocks/api/test/serializer.js b/blocks/api/test/serializer.js
index 645f670df4565..32b7ebba2eb11 100644
--- a/blocks/api/test/serializer.js
+++ b/blocks/api/test/serializer.js
@@ -25,8 +25,10 @@ describe( 'block serializer', () => {
 		context( 'function save', () => {
 			it( 'should return string verbatim', () => {
 				const saved = getSaveContent(
-					( { attributes } ) => attributes.fruit,
-					'core/fruit',
+					{
+						save: ( { attributes } ) => attributes.fruit,
+						name: 'core/fruit',
+					},
 					{ fruit: 'Bananas' }
 				);
 
@@ -35,8 +37,10 @@ describe( 'block serializer', () => {
 
 			it( 'should return element as string if save returns element', () => {
 				const saved = getSaveContent(
-					( { attributes } ) => createElement( 'div', null, attributes.fruit ),
-					'core/fruit',
+					{
+						save: ( { attributes } ) => createElement( 'div', null, attributes.fruit ),
+						name: 'core/fruit',
+					},
 					{ fruit: 'Bananas' }
 				);
 
@@ -45,24 +49,54 @@ describe( 'block serializer', () => {
 
 			it( 'should return use the namespace in the classname if it\' not a core block', () => {
 				const saved = getSaveContent(
-					( { attributes } ) => createElement( 'div', null, attributes.fruit ),
-					'myplugin/fruit',
+					{
+						save: ( { attributes } ) => createElement( 'div', null, attributes.fruit ),
+						name: 'myplugin/fruit',
+					},
 					{ fruit: 'Bananas' }
 				);
 
 				expect( saved ).to.equal( '<div class="wp-block-myplugin-fruit">Bananas</div>' );
 			} );
+
+			it( 'should overrides the className', () => {
+				const saved = getSaveContent(
+					{
+						save: ( { attributes } ) => createElement( 'div', null, attributes.fruit ),
+						name: 'myplugin/fruit',
+						className: 'apples',
+					},
+					{ fruit: 'Bananas' }
+				);
+
+				expect( saved ).to.equal( '<div class="apples">Bananas</div>' );
+			} );
+
+			it( 'should not add a className if falsy', () => {
+				const saved = getSaveContent(
+					{
+						save: ( { attributes } ) => createElement( 'div', null, attributes.fruit ),
+						name: 'myplugin/fruit',
+						className: false,
+					},
+					{ fruit: 'Bananas' }
+				);
+
+				expect( saved ).to.equal( '<div>Bananas</div>' );
+			} );
 		} );
 
 		context( 'component save', () => {
 			it( 'should return element as string', () => {
 				const saved = getSaveContent(
-					class extends Component {
-						render() {
-							return createElement( 'div', null, this.props.attributes.fruit );
-						}
+					{
+						save: class extends Component {
+							render() {
+								return createElement( 'div', null, this.props.attributes.fruit );
+							}
+						},
+						name: 'core/fruit',
 					},
-					'core/fruit',
 					{ fruit: 'Bananas' }
 				);
 
diff --git a/blocks/library/heading/index.js b/blocks/library/heading/index.js
index 05a432c667392..0619e13f071c0 100644
--- a/blocks/library/heading/index.js
+++ b/blocks/library/heading/index.js
@@ -26,6 +26,8 @@ registerBlockType( 'core/heading', {
 
 	category: 'common',
 
+	className: false,
+
 	attributes: {
 		content: children( 'h1,h2,h3,h4,h5,h6' ),
 		nodeName: prop( 'h1,h2,h3,h4,h5,h6', 'nodeName' ),
diff --git a/blocks/library/text/index.js b/blocks/library/text/index.js
index f4663ec8f34fe..4afc842abc602 100644
--- a/blocks/library/text/index.js
+++ b/blocks/library/text/index.js
@@ -23,6 +23,8 @@ registerBlockType( 'core/text', {
 
 	category: 'common',
 
+	className: false,
+
 	attributes: {
 		content: query( 'p', children() ),
 	},
diff --git a/blocks/test/fixtures/core-heading-h2-em.html b/blocks/test/fixtures/core-heading-h2-em.html
index b301eb4fbfae0..7755d1dcf4eae 100644
--- a/blocks/test/fixtures/core-heading-h2-em.html
+++ b/blocks/test/fixtures/core-heading-h2-em.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-heading">The <em>Inserter</em> Tool</h2>
+<h2>The <em>Inserter</em> Tool</h2>
 <!-- /wp:core/heading -->
diff --git a/blocks/test/fixtures/core-heading-h2-em.serialized.html b/blocks/test/fixtures/core-heading-h2-em.serialized.html
index 7fc5a6497df1c..e45d45e05d4ee 100644
--- a/blocks/test/fixtures/core-heading-h2-em.serialized.html
+++ b/blocks/test/fixtures/core-heading-h2-em.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-heading">The <em>Inserter</em> Tool</h2>
+<h2>The <em>Inserter</em> Tool</h2>
 <!-- /wp:core/heading -->
 
diff --git a/blocks/test/fixtures/core-heading-h2.html b/blocks/test/fixtures/core-heading-h2.html
index d7b487af0b670..a55b391a25057 100644
--- a/blocks/test/fixtures/core-heading-h2.html
+++ b/blocks/test/fixtures/core-heading-h2.html
@@ -1,3 +1,3 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-heading">A picture is worth a thousand words, or so the saying goes</h2>
+<h2>A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:core/heading -->
diff --git a/blocks/test/fixtures/core-heading-h2.serialized.html b/blocks/test/fixtures/core-heading-h2.serialized.html
index 437f79dbb01ce..180f05ff62466 100644
--- a/blocks/test/fixtures/core-heading-h2.serialized.html
+++ b/blocks/test/fixtures/core-heading-h2.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/heading -->
-<h2 class="wp-block-heading">A picture is worth a thousand words, or so the saying goes</h2>
+<h2>A picture is worth a thousand words, or so the saying goes</h2>
 <!-- /wp:core/heading -->
 
diff --git a/blocks/test/fixtures/core-text-align-right.html b/blocks/test/fixtures/core-text-align-right.html
index 84087f8d69135..d3d0c922ce2bf 100644
--- a/blocks/test/fixtures/core-text-align-right.html
+++ b/blocks/test/fixtures/core-text-align-right.html
@@ -1,3 +1,3 @@
 <!-- wp:core/text align="right" -->
-<p class="wp-block-text" style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
+<p style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
 <!-- /wp:core/text -->
diff --git a/blocks/test/fixtures/core-text-align-right.serialized.html b/blocks/test/fixtures/core-text-align-right.serialized.html
index e144eab376ffa..5bbeb051d3186 100644
--- a/blocks/test/fixtures/core-text-align-right.serialized.html
+++ b/blocks/test/fixtures/core-text-align-right.serialized.html
@@ -1,4 +1,4 @@
 <!-- wp:core/text align="right" -->
-<p style="text-align:right;" class="wp-block-text">... like this one, which is separate from the above and right aligned.</p>
+<p style="text-align:right;">... like this one, which is separate from the above and right aligned.</p>
 <!-- /wp:core/text -->
 

From 9a01b0f385699eaaf39f930eb588206c566fcca7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mat=C3=ADas=20Ventura?= <mv@matiasventura.com>
Date: Fri, 23 Jun 2017 16:22:26 +0200
Subject: [PATCH 4/7] Don't generate class for lists.

---
 blocks/library/list/index.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/blocks/library/list/index.js b/blocks/library/list/index.js
index 750cce361564a..a31d69daf4db2 100644
--- a/blocks/library/list/index.js
+++ b/blocks/library/list/index.js
@@ -74,6 +74,8 @@ registerBlockType( 'core/list', {
 		values: children( 'ol,ul' ),
 	},
 
+	className: false,
+
 	transforms: {
 		from: [
 			{

From 18ff8d010d9b5e0413f67afdbf90e72b7a2d7e60 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mat=C3=ADas=20Ventura?= <mv@matiasventura.com>
Date: Fri, 23 Jun 2017 16:25:13 +0200
Subject: [PATCH 5/7] Fix fixtures.

---
 blocks/test/fixtures/core-list-ul.html            | 2 +-
 blocks/test/fixtures/core-list-ul.serialized.html | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/blocks/test/fixtures/core-list-ul.html b/blocks/test/fixtures/core-list-ul.html
index 565bbe3c19c77..aef6bf669f2c9 100644
--- a/blocks/test/fixtures/core-list-ul.html
+++ b/blocks/test/fixtures/core-list-ul.html
@@ -1,3 +1,3 @@
 <!-- wp:core/list -->
-<ul class="wp-block-list"><li>Text & Headings</li><li>Images & Videos</li><li>Galleries</li><li>Embeds, like YouTube, Tweets, or other WordPress posts.</li><li>Layout blocks, like Buttons, Hero Images, Separators, etc.</li><li>And <em>Lists</em> like this one of course :)</li></ul>
+<ul><li>Text & Headings</li><li>Images & Videos</li><li>Galleries</li><li>Embeds, like YouTube, Tweets, or other WordPress posts.</li><li>Layout blocks, like Buttons, Hero Images, Separators, etc.</li><li>And <em>Lists</em> like this one of course :)</li></ul>
 <!-- /wp:core/list -->
diff --git a/blocks/test/fixtures/core-list-ul.serialized.html b/blocks/test/fixtures/core-list-ul.serialized.html
index 1496949eb48f1..f572f8fc37b11 100644
--- a/blocks/test/fixtures/core-list-ul.serialized.html
+++ b/blocks/test/fixtures/core-list-ul.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/list -->
-<ul class="wp-block-list">
+<ul>
     <li>Text &amp; Headings</li>
     <li>Images &amp; Videos</li>
     <li>Galleries</li>

From 724071773aac48f1f014a15f98703de763846c79 Mon Sep 17 00:00:00 2001
From: Riad Benguella <benguella@gmail.com>
Date: Fri, 23 Jun 2017 15:30:03 +0100
Subject: [PATCH 6/7] Serializer: Fix cover image and html blocks' tests after
 rebasing

---
 blocks/library/html/index.js                          | 2 ++
 blocks/test/fixtures/core-cover-image.serialized.html | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/blocks/library/html/index.js b/blocks/library/html/index.js
index bc5c05b4a84cd..554781c834cad 100644
--- a/blocks/library/html/index.js
+++ b/blocks/library/html/index.js
@@ -25,6 +25,8 @@ registerBlockType( 'core/html', {
 
 	category: 'formatting',
 
+	className: false,
+
 	attributes: {
 		content: children(),
 	},
diff --git a/blocks/test/fixtures/core-cover-image.serialized.html b/blocks/test/fixtures/core-cover-image.serialized.html
index 7e8bcbb7014ad..c4858e6d55089 100644
--- a/blocks/test/fixtures/core-cover-image.serialized.html
+++ b/blocks/test/fixtures/core-cover-image.serialized.html
@@ -1,5 +1,5 @@
 <!-- wp:core/cover-image url="https://cldup.com/uuUqE_dXzy.jpg" -->
-<section class="blocks-cover-image">
+<section class="blocks-cover-image wp-block-cover-image">
     <section class="cover-image" style="background-image:url(https://cldup.com/uuUqE_dXzy.jpg);">
         <h2>Guten Berg!</h2>
     </section>

From b15b00f65d182e43999124e99d8435b2e958394b Mon Sep 17 00:00:00 2001
From: Riad Benguella <benguella@gmail.com>
Date: Fri, 23 Jun 2017 15:34:07 +0100
Subject: [PATCH 7/7] Plugin: update the default post content with the
 automatically generated classnames

---
 post-content.js | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/post-content.js b/post-content.js
index 3f4b930161869..17d8d6b298329 100644
--- a/post-content.js
+++ b/post-content.js
@@ -9,7 +9,7 @@ window._wpGutenbergPost = {
 	content: {
 		raw: [
 			'<!-- wp:core/cover-image url="https://cldup.com/GCwahb3aOb.jpg" -->',
-			'<section className="cover-image" style={ { backgroundImage: \'url("https://cldup.com/GCwahb3aOb.jpg");\' } }><h2>Gutenberg Editor</h2></section>',
+			'<section className="cover-image wp-block-cover-image" style={ { backgroundImage: \'url("https://cldup.com/GCwahb3aOb.jpg");\' } }><h2>Gutenberg Editor</h2></section>',
 			'<!-- /wp:core/cover-image -->',
 
 			'<!-- wp:core/text data="{\\"projectName\\":\\"gutenberg\\",\\"isAwesome\\":true}" -->',
@@ -39,7 +39,7 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/text -->',
 
 			'<!-- wp:core/image align="center" -->',
-			'<figure><img alt="Beautiful landscape" src="https://cldup.com/YLYhpou2oq.jpg" class="aligncenter"/><figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption></figure>',
+			'<figure class="wp-block-image"><img alt="Beautiful landscape" src="https://cldup.com/YLYhpou2oq.jpg" class="aligncenter"/><figcaption>Give it a try. Press the &quot;really wide&quot; button on the image toolbar.</figcaption></figure>',
 			'<!-- /wp:core/image -->',
 
 			'<!-- wp:core/text -->',
@@ -67,11 +67,11 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/text -->',
 
 			'<!-- wp:core/button align="center" -->',
-			'<div class="aligncenter"><a href="https://github.com/WordPress/gutenberg"><span>Help build Gutenberg</span></a></div>',
+			'<div class="aligncenter wp-block-button"><a href="https://github.com/WordPress/gutenberg"><span>Help build Gutenberg</span></a></div>',
 			'<!-- /wp:core/button -->',
 
 			'<!-- wp:core/separator -->',
-			'<hr/>',
+			'<hr class="wp-block-separator" />',
 			'<!-- /wp:core/separator -->',
 
 			'<!-- wp:core/heading -->',
@@ -83,7 +83,7 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/text -->',
 
 			'<!-- wp:core/quote style="1" -->',
-			'<blockquote class="blocks-quote-style-1"><p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p><footer>Matt Mullenweg, 2017</footer></blockquote>',
+			'<blockquote class="blocks-quote-style-1 wp-block-quote"><p>The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery.</p><footer>Matt Mullenweg, 2017</footer></blockquote>',
 			'<!-- /wp:core/quote -->',
 
 			'<!-- wp:core/text -->',
@@ -95,11 +95,11 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/text -->',
 
 			'<!-- wp:core/quote style="2" -->',
-			'<blockquote class="blocks-quote-style-2"><p>There is no greater agony than bearing an untold story inside you.</p><footer>Maya Angelou</footer></blockquote>',
+			'<blockquote class="blocks-quote-style-2 wp-block-quote"><p>There is no greater agony than bearing an untold story inside you.</p><footer>Maya Angelou</footer></blockquote>',
 			'<!-- /wp:core/quote -->',
 
 			'<!-- wp:core/separator -->',
-			'<hr/>',
+			'<hr class="wp-block-separator" />',
 			'<!-- /wp:core/separator -->',
 
 			'<!-- wp:core/heading -->',
@@ -111,7 +111,7 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/text -->',
 
 			'<!-- wp:core/image -->',
-			'<figure><img alt="Accessibility is important don\'t forget image alt attribute" src="https://cldup.com/uuUqE_dXzy.jpg" /></figure>',
+			'<figure class="wp-block-image"><img alt="Accessibility is important don\'t forget image alt attribute" src="https://cldup.com/uuUqE_dXzy.jpg" /></figure>',
 			'<!-- /wp:core/image -->',
 
 			'<!-- wp:core/text -->',
@@ -123,21 +123,21 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/text -->',
 
 			'<!-- wp:core/code -->',
-			'<pre><code>export default function MyButton() {\n\
+			'<pre class="wp-block-code"><code>export default function MyButton() {\n\
 	return &lt;Button&gt;Click Me!&lt;/Button&gt;;\n\
 }</code></pre>',
 			'<!-- /wp:core/code -->',
 
 			'<!-- wp:core/image -->',
-			'<figure><img alt="Yet another image block" src="https://cldup.com/GCwahb3aOb.jpg" /></figure>',
+			'<figure class="wp-block-image"><img alt="Yet another image block" src="https://cldup.com/GCwahb3aOb.jpg" /></figure>',
 			'<!-- /wp:core/image -->',
 
 			'<!-- wp:core/image -->',
-			'<figure><img alt="Yet another image block" src="https://cldup.com/lUUQPv6w9c.jpg" /></figure>',
+			'<figure class="wp-block-image"><img alt="Yet another image block" src="https://cldup.com/lUUQPv6w9c.jpg" /></figure>',
 			'<!-- /wp:core/image -->',
 
 			'<!-- wp:core/preformatted -->',
-			'<pre>An old silent pond...<br>A frog jumps into the pond,<br>splash! Silence again.</pre>',
+			'<pre class="wp-block-preformatted">An old silent pond...<br>A frog jumps into the pond,<br>splash! Silence again.</pre>',
 			'<!-- /wp:core/preformatted -->',
 
 			'<!-- wp:core/text -->',
@@ -153,15 +153,15 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/list -->',
 
 			'<!-- wp:core/pullquote -->',
-			'<blockquote class="blocks-pullquote"><p>Code is Poetry</p><footer>The WordPress community</footer></blockquote>',
+			'<blockquote class="blocks-pullquote wp-block-pullquote"><p>Code is Poetry</p><footer>The WordPress community</footer></blockquote>',
 			'<!-- /wp:core/pullquote -->',
 
 			'<!-- wp:core/separator -->',
-			'<hr/>',
+			'<hr class="wp-block-separator" />',
 			'<!-- /wp:core/separator -->',
 
 			'<!-- wp:core/table -->',
-			'<table class="widefat"><thead><tr><th>Version</th><th>Musician</th><th>Date</th></tr></thead><tbody><tr><th><a href="https://wordpress.org/news/2015/12/clifford/">4.4</a></th><td>Clifford Brown</td><td>December 8, 2015</td></tr><tr class="alt"><th><a href="https://wordpress.org/news/2016/04/coleman/">4.5</a></th><td>Coleman Hawkins</td><td>April 12, 2016</td></tr><tr><th><a href="https://wordpress.org/news/2016/08/pepper/">4.6</a></th><td>Pepper Adams</td><td>August 16, 2016</td></tr><tr class="alt"><th><a href="https://wordpress.org/news/2016/12/vaughan/">4.7</a></th><td>Sarah Vaughan</td><td>December 6, 2016</td></tr></tbody></table>',
+			'<table class="widefat wp-block-table"><thead><tr><th>Version</th><th>Musician</th><th>Date</th></tr></thead><tbody><tr><th><a href="https://wordpress.org/news/2015/12/clifford/">4.4</a></th><td>Clifford Brown</td><td>December 8, 2015</td></tr><tr class="alt"><th><a href="https://wordpress.org/news/2016/04/coleman/">4.5</a></th><td>Coleman Hawkins</td><td>April 12, 2016</td></tr><tr><th><a href="https://wordpress.org/news/2016/08/pepper/">4.6</a></th><td>Pepper Adams</td><td>August 16, 2016</td></tr><tr class="alt"><th><a href="https://wordpress.org/news/2016/12/vaughan/">4.7</a></th><td>Sarah Vaughan</td><td>December 6, 2016</td></tr></tbody></table>',
 			'<!-- /wp:core/table -->',
 
 			'<!-- wp:core/heading -->',
@@ -169,7 +169,7 @@ window._wpGutenbergPost = {
 			'<!-- /wp:core/heading -->',
 
 			'<!-- wp:core/embed url="https://www.youtube.com/watch?v=Nl6U7UotA-M" -->',
-			'<figure>https://www.youtube.com/watch?v=Nl6U7UotA-M<figcaption>State of the Word 2016</figcaption></figure>',
+			'<figure class="wp-block-embed">https://www.youtube.com/watch?v=Nl6U7UotA-M<figcaption>State of the Word 2016</figcaption></figure>',
 			'<!-- /wp:core/embed -->',
 
 			'<!-- wp:core/embed url="https://twitter.com/photomatt/status/868657763970404352" -->',