diff --git a/.travis.yml b/.travis.yml
index a9652ccc33e4ac..076ccfd0249468 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,65 @@
-language: node_js
-node_js:
-  - "node"
+sudo: false
+
+language: php
+
+notifications:
+  email:
+    on_success: never
+    on_failure: change
+
+cache:
+  directories:
+    - vendor
+    - $HOME/.composer/cache
+
+before_install:
+  - nvm install 7 && nvm use 7
+
+matrix:
+  include:
+    - php: 7.1
+      env: WP_VERSION=latest
+    - php: 5.6
+      env: WP_VERSION=latest
+    - php: 5.2
+      env: WP_VERSION=latest
+    - php: 5.6
+      env: TRAVISCI=phpcs
+    - php: 7.1
+      env: TRAVISCI=js
+
+before_script:
+  - export PATH="$HOME/.composer/vendor/bin:$PATH"
+  - |
+    if [[ ! -z "$WP_VERSION" ]] ; then
+      bash bin/install-wp-tests.sh wordpress_test root '' localhost $WP_VERSION
+      if [[ ${TRAVIS_PHP_VERSION:0:2} == "5." ]]; then
+        mkdir -p $HOME/phpunit-bin
+        wget -O $HOME/phpunit-bin/phpunit https://phar.phpunit.de/phpunit-4.8.phar
+        chmod +x $HOME/phpunit-bin/phpunit
+        export PATH=$PATH:$HOME/phpunit-bin/
+      else
+        composer global require "phpunit/phpunit=5.7.*"
+      fi
+    fi
+  - |
+    if [[ "$TRAVISCI" == "phpcs" ]] ; then
+      composer global require wp-coding-standards/wpcs
+      phpcs --config-set installed_paths $HOME/.composer/vendor/wp-coding-standards/wpcs
+    fi
+
 script:
-  - "npm run ci"
+  - |
+    if [[ ! -z "$WP_VERSION" ]] ; then
+      phpunit
+      WP_MULTISITE=1 phpunit
+    fi
+  - |
+    if [[ "$TRAVISCI" == "phpcs" ]] ; then
+      phpcs --standard=phpcs.ruleset.xml $(find . -name '*.php')
+    fi
+  - |
+    if [[ "$TRAVISCI" == "js" ]] ; then
+      npm install
+      npm run ci
+    fi
diff --git a/bin/install-wp-tests.sh b/bin/install-wp-tests.sh
new file mode 100755
index 00000000000000..73bb4c787eb2cc
--- /dev/null
+++ b/bin/install-wp-tests.sh
@@ -0,0 +1,127 @@
+#!/usr/bin/env bash
+
+if [ $# -lt 3 ]; then
+	echo "usage: $0 <db-name> <db-user> <db-pass> [db-host] [wp-version] [skip-database-creation]"
+	exit 1
+fi
+
+DB_NAME=$1
+DB_USER=$2
+DB_PASS=$3
+DB_HOST=${4-localhost}
+WP_VERSION=${5-latest}
+SKIP_DB_CREATE=${6-false}
+
+WP_TESTS_DIR=${WP_TESTS_DIR-/tmp/wordpress-tests-lib}
+WP_CORE_DIR=${WP_CORE_DIR-/tmp/wordpress/}
+
+download() {
+    if [ `which curl` ]; then
+        curl -s "$1" > "$2";
+    elif [ `which wget` ]; then
+        wget -nv -O "$2" "$1"
+    fi
+}
+
+if [[ $WP_VERSION =~ [0-9]+\.[0-9]+(\.[0-9]+)? ]]; then
+	WP_TESTS_TAG="tags/$WP_VERSION"
+elif [[ $WP_VERSION == 'nightly' || $WP_VERSION == 'trunk' ]]; then
+	WP_TESTS_TAG="trunk"
+else
+	# http serves a single offer, whereas https serves multiple. we only want one
+	download http://api.wordpress.org/core/version-check/1.7/ /tmp/wp-latest.json
+	grep '[0-9]+\.[0-9]+(\.[0-9]+)?' /tmp/wp-latest.json
+	LATEST_VERSION=$(grep -o '"version":"[^"]*' /tmp/wp-latest.json | sed 's/"version":"//')
+	if [[ -z "$LATEST_VERSION" ]]; then
+		echo "Latest WordPress version could not be found"
+		exit 1
+	fi
+	WP_TESTS_TAG="tags/$LATEST_VERSION"
+fi
+
+set -ex
+
+install_wp() {
+
+	if [ -d $WP_CORE_DIR ]; then
+		return;
+	fi
+
+	mkdir -p $WP_CORE_DIR
+
+	if [[ $WP_VERSION == 'nightly' || $WP_VERSION == 'trunk' ]]; then
+		mkdir -p /tmp/wordpress-nightly
+		download https://wordpress.org/nightly-builds/wordpress-latest.zip  /tmp/wordpress-nightly/wordpress-nightly.zip
+		unzip -q /tmp/wordpress-nightly/wordpress-nightly.zip -d /tmp/wordpress-nightly/
+		mv /tmp/wordpress-nightly/wordpress/* $WP_CORE_DIR
+	else
+		if [ $WP_VERSION == 'latest' ]; then
+			local ARCHIVE_NAME='latest'
+		else
+			local ARCHIVE_NAME="wordpress-$WP_VERSION"
+		fi
+		download https://wordpress.org/${ARCHIVE_NAME}.tar.gz  /tmp/wordpress.tar.gz
+		tar --strip-components=1 -zxmf /tmp/wordpress.tar.gz -C $WP_CORE_DIR
+	fi
+
+	download https://raw.github.com/markoheijnen/wp-mysqli/master/db.php $WP_CORE_DIR/wp-content/db.php
+}
+
+install_test_suite() {
+	# portable in-place argument for both GNU sed and Mac OSX sed
+	if [[ $(uname -s) == 'Darwin' ]]; then
+		local ioption='-i .bak'
+	else
+		local ioption='-i'
+	fi
+
+	# set up testing suite if it doesn't yet exist
+	if [ ! -d $WP_TESTS_DIR ]; then
+		# set up testing suite
+		mkdir -p $WP_TESTS_DIR
+		svn co --quiet https://develop.svn.wordpress.org/${WP_TESTS_TAG}/tests/phpunit/includes/ $WP_TESTS_DIR/includes
+		svn co --quiet https://develop.svn.wordpress.org/${WP_TESTS_TAG}/tests/phpunit/data/ $WP_TESTS_DIR/data
+	fi
+
+	if [ ! -f wp-tests-config.php ]; then
+		download https://develop.svn.wordpress.org/${WP_TESTS_TAG}/wp-tests-config-sample.php "$WP_TESTS_DIR"/wp-tests-config.php
+		# remove all forward slashes in the end
+		WP_CORE_DIR=$(echo $WP_CORE_DIR | sed "s:/\+$::")
+		sed $ioption "s:dirname( __FILE__ ) . '/src/':'$WP_CORE_DIR/':" "$WP_TESTS_DIR"/wp-tests-config.php
+		sed $ioption "s/youremptytestdbnamehere/$DB_NAME/" "$WP_TESTS_DIR"/wp-tests-config.php
+		sed $ioption "s/yourusernamehere/$DB_USER/" "$WP_TESTS_DIR"/wp-tests-config.php
+		sed $ioption "s/yourpasswordhere/$DB_PASS/" "$WP_TESTS_DIR"/wp-tests-config.php
+		sed $ioption "s|localhost|${DB_HOST}|" "$WP_TESTS_DIR"/wp-tests-config.php
+	fi
+
+}
+
+install_db() {
+
+	if [ ${SKIP_DB_CREATE} = "true" ]; then
+		return 0
+	fi
+
+	# parse DB_HOST for port or socket references
+	local PARTS=(${DB_HOST//\:/ })
+	local DB_HOSTNAME=${PARTS[0]};
+	local DB_SOCK_OR_PORT=${PARTS[1]};
+	local EXTRA=""
+
+	if ! [ -z $DB_HOSTNAME ] ; then
+		if [ $(echo $DB_SOCK_OR_PORT | grep -e '^[0-9]\{1,\}$') ]; then
+			EXTRA=" --host=$DB_HOSTNAME --port=$DB_SOCK_OR_PORT --protocol=tcp"
+		elif ! [ -z $DB_SOCK_OR_PORT ] ; then
+			EXTRA=" --socket=$DB_SOCK_OR_PORT"
+		elif ! [ -z $DB_HOSTNAME ] ; then
+			EXTRA=" --host=$DB_HOSTNAME --protocol=tcp"
+		fi
+	fi
+
+	# create database
+	mysqladmin create $DB_NAME --user="$DB_USER" --password="$DB_PASS"$EXTRA
+}
+
+install_wp
+install_test_suite
+install_db
diff --git a/index.php b/index.php
index 633db0559ddce9..7f7a6746c55a4b 100644
--- a/index.php
+++ b/index.php
@@ -33,10 +33,10 @@ function gutenberg_menu() {
 /**
  * Registers a block.
  *
- * @param  string   $slug     Block slug including namespace.
- * @param  array    $settings Block settings
+ * @param  string $slug Block slug including namespace.
+ * @param  array  $settings Block settings.
 
- * @return array              The block, if it has been successfully registered.
+ * @return array            The block, if it has been successfully registered.
  */
 function register_block( $slug, $settings ) {
 	global $registered_blocks;
@@ -55,23 +55,39 @@ function register_block( $slug, $settings ) {
 	}
 
 	if ( isset( $registered_blocks[ $slug ] ) ) {
-		$message = sprintf( __( 'Block "%s" is already registered.' ), $slug );
-		_doing_it_wrong( __FUNCTION__, $message, '0.1.0' );
 		return;
 	}
 
-	$settings[ 'slug' ] = $slug;
+	$settings['slug'] = $slug;
 	$registered_blocks[ $slug ] = $settings;
 
 	return $settings;
 }
 
+/**
+ * Unregisters a block.
+ *
+ * @param  string $slug Block slug.
+ * @return array        The previous block value, if it has been
+ *                        successfully unregistered; otherwise `null`.
+ */
+function unregister_block( $slug ) {
+	global $registered_blocks;
+	if ( ! isset( $registered_blocks[ $slug ] ) ) {
+		/* translators: 1: block slug */
+		$message = sprintf( __( 'Block "%s" is not registered.' ), $slug );
+		_doing_it_wrong( __FUNCTION__, $message, '0.1.0' );
+		return;
+	}
+	unset( $registered_blocks[ $slug ] );
+}
+
 /**
  * Extract the block attributes from the block's attributes string
  *
  * @since 0.1.0
  *
- * @param  string $attr_string Attributes string
+ * @param string $attr_string Attributes string.
 
  * @return array
  */
@@ -79,8 +95,8 @@ function parse_block_attributes( $attr_string ) {
 	$attributes_matcher = '/([^\s]+):([^\s]+)\s*/';
 	preg_match_all( $attributes_matcher, $attr_string, $matches );
 	$attributes = array();
-	foreach ( $matches[ 1 ] as $index => $attribute_match ) {
-		$attributes[ $attribute_match ] = $matches[ 2 ][ $index ];
+	foreach ( $matches[1] as $index => $attribute_match ) {
+		$attributes[ $attribute_match ] = $matches[2][ $index ];
 	}
 
 	return $attributes;
@@ -91,40 +107,40 @@ function parse_block_attributes( $attr_string ) {
  *
  * @since 0.1.0
  *
- * @param  string $content Post content
-
- * @return string          Updated post content
+ * @param  string $content Post content.
+ *
+ * @return string          Updated post content.
  */
 function do_blocks( $content ) {
 	global $registered_blocks;
 
-	// Extract the blocks from the post content
-	$open_matcher = '/<!--\s*wp:([a-z](?:[a-z0-9\/]+)*)\s+((?:(?!-->).)*)-->.*<!--\s*\/wp:\g1\s+-->/';
+	// Extract the blocks from the post content.
+	$open_matcher = '/<!--\s*wp:([a-z](?:[a-z0-9\/]+)*)\s+((?:(?!-->).)*)-->.*?<!--\s*\/wp:\g1\s+-->/';
 	preg_match_all( $open_matcher, $content, $matches, PREG_OFFSET_CAPTURE );
 
 	$new_content = $content;
-	foreach ( $matches[ 0 ] as $index => $block_match ) {
-		$block_name = $matches[ 1 ][ $index ][ 0 ];
-		// do nothing if the block is not registered
+	foreach ( $matches[0] as $index => $block_match ) {
+		$block_name = $matches[1][ $index ][0];
+		// do nothing if the block is not registered.
 		if ( ! isset( $registered_blocks[ $block_name ] ) ) {
 			continue;
 		}
 
-		$block_markup = $block_match[ 0 ];
-		$block_position = $block_match[ 1 ];
-		$block_attributes_string = $matches[ 2 ][ $index ][ 0 ];
+		$block_markup = $block_match[0];
+		$block_position = $block_match[1];
+		$block_attributes_string = $matches[2][ $index ][0];
 		$block_attributes = parse_block_attributes( $block_attributes_string );
 
-		// Call the block's render function to generate the dynamic output
-		$output = call_user_func( $registered_blocks[ $block_name ][ 'render' ], $block_attributes );
+		// Call the block's render function to generate the dynamic output.
+		$output = call_user_func( $registered_blocks[ $block_name ]['render'], $block_attributes );
 
-		// Replace the matched block with the dynamic output
+		// Replace the matched block with the dynamic output.
 		$new_content = str_replace( $block_markup, $output, $new_content );
 	}
 
 	return $new_content;
 }
-add_filter( 'the_content', 'do_blocks', 10 ); // BEFORE do_shortcode()
+add_filter( 'the_content', 'do_blocks', 10 ); // BEFORE do_shortcode().
 
 /**
  * Registers common scripts to be used as dependencies of the editor and plugins.
@@ -158,9 +174,9 @@ function gutenberg_register_scripts() {
  * @since 0.1.0
  */
 function gutenberg_add_edit_links_filters() {
-	// For hierarchical post types
+	// For hierarchical post types.
 	add_filter( 'page_row_actions', 'gutenberg_add_edit_links', 10, 2 );
-	// For non-hierarchical post types
+	// For non-hierarchical post types.
 	add_filter( 'post_row_actions', 'gutenberg_add_edit_links', 10, 2 );
 }
 add_action( 'admin_init', 'gutenberg_add_edit_links_filters' );
@@ -170,14 +186,18 @@ function gutenberg_add_edit_links_filters() {
  * the Gutenberg editor.
  *
  * @since 0.1.0
+ *
+ * @param  array $actions Post actions.
+ * @param  array $post    Edited post.
+ *
+ * @return array          Updated post actions.
  */
 function gutenberg_add_edit_links( $actions, $post ) {
 	$can_edit_post = current_user_can( 'edit_post', $post->ID );
 	$title = _draft_or_post_title( $post->ID );
 
 	if ( $can_edit_post && 'trash' !== $post->post_status ) {
-		// Build the Gutenberg edit action.  See also:
-		// WP_Posts_List_Table::handle_row_actions()
+		// Build the Gutenberg edit action. See also: WP_Posts_List_Table::handle_row_actions().
 		$gutenberg_url = menu_page_url( 'gutenberg', false );
 		$gutenberg_action = sprintf(
 			'<a href="%s" aria-label="%s">%s</a>',
@@ -193,7 +213,9 @@ function gutenberg_add_edit_links( $actions, $post ) {
 		$edit_offset = array_search( 'edit', array_keys( $actions ), true );
 		$actions = array_merge(
 			array_slice( $actions, 0, $edit_offset + 1 ),
-			array( 'gutenberg hide-if-no-js' => $gutenberg_action ),
+			array(
+				'gutenberg hide-if-no-js' => $gutenberg_action,
+			),
 			array_slice( $actions, $edit_offset + 1 )
 		);
 	}
@@ -206,6 +228,8 @@ function gutenberg_add_edit_links( $actions, $post ) {
  *
  * @since 0.1.0
  *
+ * @param  string $domain Translation domain.
+ *
  * @return array
  */
 function gutenberg_get_jed_locale_data( $domain ) {
@@ -217,10 +241,10 @@ function gutenberg_get_jed_locale_data( $domain ) {
 			$domain => array(
 				'' => array(
 					'domain' => $domain,
-					'lang'   => is_admin() ? get_user_locale() : get_locale()
-				)
-			)
-		)
+					'lang'   => is_admin() ? get_user_locale() : get_locale(),
+				),
+			),
+		),
 	);
 
 	if ( ! empty( $translations->headers['Plural-Forms'] ) ) {
@@ -253,16 +277,16 @@ function gutenberg_scripts_and_styles( $hook ) {
 	 * Scripts
 	 */
 
-	// The editor code itself
+	// The editor code itself.
 	wp_enqueue_script(
 		'wp-editor',
 		plugins_url( 'editor/build/index.js', __FILE__ ),
 		array( 'wp-i18n', 'wp-blocks', 'wp-element' ),
 		filemtime( plugin_dir_path( __FILE__ ) . 'editor/build/index.js' ),
-		true   // $in_footer
+		true // enqueue in the footer.
 	);
 
-	// Load an actual post if an ID is specified
+	// Load an actual post if an ID is specified.
 	$post_to_edit = null;
 	if ( isset( $_GET['post_id'] ) && (int) $_GET['post_id'] > 0 ) {
 		$request = new WP_REST_Request(
@@ -289,7 +313,7 @@ function gutenberg_scripts_and_styles( $hook ) {
 		);
 	}
 
-	// Prepare Jed locale data
+	// Prepare Jed locale data.
 	$locale_data = gutenberg_get_jed_locale_data( 'gutenberg' );
 	wp_add_inline_script(
 		'wp-editor',
@@ -297,7 +321,7 @@ function gutenberg_scripts_and_styles( $hook ) {
 		'before'
 	);
 
-	// Initialize the editor
+	// Initialize the editor.
 	wp_add_inline_script( 'wp-editor', 'wp.editor.createEditorInstance( \'editor\', _wpGutenbergPost );' );
 
 	/**
@@ -346,11 +370,3 @@ function the_gutenberg_project() {
 	</div>
 	<?php
 }
-
-function render_html_block( $attributes ) {
-	return 'THIS IS AWESOME';
-}
-
-register_block( 'core/html', array(
-	'render' => 'render_html_block'
-) );
diff --git a/phpcs.ruleset.xml b/phpcs.ruleset.xml
new file mode 100644
index 00000000000000..210c25a14e74ac
--- /dev/null
+++ b/phpcs.ruleset.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0"?>
+<ruleset name="WordPress Coding Standards for Plugins">
+	<description>Generally-applicable sniffs for WordPress plugins</description>
+
+	<rule ref="WordPress-Core" />
+	<rule ref="WordPress-Docs" />
+
+	<exclude-pattern>*/node_modules/*</exclude-pattern>
+	<exclude-pattern>*/vendor/*</exclude-pattern>
+</ruleset>
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
new file mode 100644
index 00000000000000..2eb5f4eae3c4b8
--- /dev/null
+++ b/phpunit.xml.dist
@@ -0,0 +1,14 @@
+<phpunit
+	bootstrap="phpunit/bootstrap.php"
+	backupGlobals="false"
+	colors="true"
+	convertErrorsToExceptions="true"
+	convertNoticesToExceptions="true"
+	convertWarningsToExceptions="true"
+	>
+	<testsuites>
+		<testsuite>
+			<directory suffix="-test.php">./phpunit/</directory>
+		</testsuite>
+	</testsuites>
+</phpunit>
diff --git a/phpunit/bootstrap.php b/phpunit/bootstrap.php
new file mode 100644
index 00000000000000..a398feb4fa5fea
--- /dev/null
+++ b/phpunit/bootstrap.php
@@ -0,0 +1,25 @@
+<?php
+/**
+ * PHPUnit bootstrap file
+ *
+ * @package Gutenberg
+ */
+
+$_tests_dir = getenv( 'WP_TESTS_DIR' );
+if ( ! $_tests_dir ) {
+	$_tests_dir = '/tmp/wordpress-tests-lib';
+}
+
+// Give access to tests_add_filter() function.
+require_once $_tests_dir . '/includes/functions.php';
+
+/**
+ * Manually load the plugin being tested.
+ */
+function _manually_load_plugin() {
+	require dirname( dirname( __FILE__ ) ) . '/index.php';
+}
+tests_add_filter( 'muplugins_loaded', '_manually_load_plugin' );
+
+// Start up the WP testing environment.
+require $_tests_dir . '/includes/bootstrap.php';
diff --git a/phpunit/class-dynamic-blocks-render-test.php b/phpunit/class-dynamic-blocks-render-test.php
new file mode 100644
index 00000000000000..a7c01439ccf2d6
--- /dev/null
+++ b/phpunit/class-dynamic-blocks-render-test.php
@@ -0,0 +1,51 @@
+<?php
+/**
+ * Dynamic blocks rendering Test
+ *
+ * @package Gutenberg
+ */
+
+/**
+ * Test do_blocks
+ */
+class Dynamic_Blocks_Render_Test extends WP_UnitTestCase {
+	/**
+	 * Dummy block rendering function.
+	 *
+	 * @param  array $attributes Block attributes.
+	 *
+	 * @return string             Block output.
+	 */
+	function render_dummy_block( $attributes ) {
+		return $attributes['value'];
+	}
+
+	/**
+	 * Successfull dynamic block rendering
+	 */
+	function test_register_block() {
+		$settings = array(
+			'render' => array(
+				$this,
+				'render_dummy_block',
+			),
+		);
+		register_block( 'core/dummy', $settings );
+		$post_content =
+			'before' .
+			'<!-- wp:core/dummy value:b1 --><!-- /wp:core/dummy -->' .
+			'between' .
+			'<!-- wp:core/dummy value:b2 --><!-- /wp:core/dummy -->' .
+			'after';
+
+		$updated_post_content = do_blocks( $post_content );
+		unregister_block( 'core/dummy' );
+		$this->assertEquals( $updated_post_content,
+			'before' .
+			'b1' .
+			'between' .
+			'b2' .
+			'after'
+		);
+	}
+}
diff --git a/phpunit/class-registration-test.php b/phpunit/class-registration-test.php
new file mode 100644
index 00000000000000..08b86e58fe394f
--- /dev/null
+++ b/phpunit/class-registration-test.php
@@ -0,0 +1,44 @@
+<?php
+/**
+ * Blocks registration Tests
+ *
+ * @package Gutenberg
+ */
+
+/**
+ * Test register_block
+ */
+class Registration_Test extends WP_UnitTestCase {
+	/**
+	 * The block slug should be a string
+	 *
+	 * @expectedIncorrectUsage register_block
+	 */
+	function test_invalid_non_string_slugs() {
+		register_block( 1, array() );
+	}
+
+	/**
+	 * The block slug should have a namespace
+	 *
+	 * @expectedIncorrectUsage register_block
+	 */
+	function test_invalid_slugs_without_namespace() {
+		register_block( 'text', array() );
+	}
+
+	/**
+	 * Successfull block registration
+	 */
+	function test_register_block() {
+		$settings = array(
+			'icon' => 'text',
+		);
+		$updated_settings = register_block( 'core/text', $settings );
+		$this->assertEquals( $updated_settings, array(
+			'icon' => 'text',
+			'slug' => 'core/text',
+		) );
+		unregister_block( 'core/text' );
+	}
+}