diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-themes-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-themes-controller.php
index 47491e7774..bc5764d268 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-themes-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-themes-controller.php
@@ -106,14 +106,25 @@ class WP_REST_Themes_Controller extends WP_REST_Controller {
 		$fields = $this->get_fields_for_response( $request );
 
 		if ( in_array( 'theme_supports', $fields, true ) ) {
+			$item_schemas   = $this->get_item_schema();
+			$theme_supports = $item_schemas['properties']['theme_supports']['properties'];
+			foreach ( $theme_supports as $name => $schema ) {
+				$data['theme_supports'][ $name ] = rest_sanitize_value_from_schema( get_theme_support( $name ), $schema );
+				if ( array( 'array', 'bool' ) === $schema['type']   ) {
+					if ( is_array( $data['theme_supports'][ $name ] ) && ! empty( $data['theme_supports'][ $name ] ) ) {
+						$data['theme_supports'][ $name ] = array_shift( $data['theme_supports'][ $name ] );
+					} else {
+						$data['theme_supports'][ $name ] = (bool) $data['theme_supports'][ $name ];
+					}
+				}
+			}
+
 			$formats                           = get_theme_support( 'post-formats' );
 			$formats                           = is_array( $formats ) ? array_values( $formats[0] ) : array();
 			$formats                           = array_merge( array( 'standard' ), $formats );
 			$data['theme_supports']['formats'] = $formats;
 
-			$data['theme_supports']['post-thumbnails']   = false;
-			$data['theme_supports']['responsive-embeds'] = (bool) get_theme_support( 'responsive-embeds' );
-			$post_thumbnails                             = get_theme_support( 'post-thumbnails' );
+			$post_thumbnails = get_theme_support( 'post-thumbnails' );
 
 			if ( $post_thumbnails ) {
 				// $post_thumbnails can contain a nested array of post types.
@@ -161,21 +172,204 @@ class WP_REST_Themes_Controller extends WP_REST_Controller {
 					'type'        => 'array',
 					'readonly'    => true,
 					'properties'  => array(
-						'formats'           => array(
+						'align-wide'                => array(
+							'description' => __( 'Whether theme opts in to wide alignment CSS class.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'automatic-feed-links'      => array(
+							'description' => __( 'Whether posts and comments RSS feed links are added to head.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'custom-header'             => array(
+							'description' => __( 'Custom header if defined by the theme.' ),
+							'type'        => array( 'array', 'bool' ),
+							'items'       => array(
+								'type'       => 'object',
+								'properties' => array(
+									'default-image'       => array(
+										'type' => 'string',
+									),
+									'random-default'      => array(
+										'type' => 'bool',
+									),
+									'width'               => array(
+										'type' => 'number',
+									),
+									'height'              => array(
+										'type' => 'number',
+									),
+									'flex-height'         => array(
+										'type' => 'bool',
+									),
+									'flex-width'          => array(
+										'type' => 'bool',
+									),
+									'default-text-color'  => array(
+										'type' => 'string',
+									),
+									'header-text'         => array(
+										'type' => 'bool',
+									),
+									'uploads'             => array(
+										'type' => 'bool',
+									),
+									'wp-head-callback'    => array(
+										'type' => 'string',
+									),
+									'admin-head-callback' => array(
+										'type' => 'string',
+									),
+									'admin-preview-callback' => array(
+										'type' => 'string',
+									),
+									'video'               => array(
+										'type' => 'bool',
+									),
+									'video-active-callback' => array(
+										'type' => 'string',
+									),
+								),
+							),
+							'readonly'    => true,
+						),
+						'custom-logo'               => array(
+							'description' => __( 'Custom logo if defined by the theme.' ),
+							'type'        => array( 'array', 'bool' ),
+							'items'       => array(
+								'type'       => 'object',
+								'properties' => array(
+									'width'       => array(
+										'type' => 'number',
+									),
+									'height'      => array(
+										'type' => 'number',
+									),
+									'flex-width'  => array(
+										'type' => 'bool',
+									),
+									'flex-height' => array(
+										'type' => 'bool',
+									),
+									'header-text' => array(
+										'type' => 'array',
+									),
+								),
+							),
+							'readonly'    => true,
+						),
+						'customize-selective-refresh-widgets' => array(
+							'description' => __( 'Whether the theme enables Selective Refresh for Widgets being managed with the Customizer.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'dark-editor-style'         => array(
+							'description' => __( 'Whether theme opts in to the dark editor style UI.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'disable-custom-colors'     => array(
+							'description' => __( 'Whether the theme disables custom colors.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'disable-custom-font-sizes' => array(
+							'description' => __( 'Whether the theme disables custom font sizes.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'editor-color-palette'      => array(
+							'description' => __( 'Custom color palette if defined by the theme.' ),
+							'type'        => array( 'array', 'bool' ),
+							'items'       => array(
+								'type'       => 'object',
+								'properties' => array(
+									'name'  => array(
+										'type' => 'string',
+									),
+									'slug'  => array(
+										'type' => 'string',
+									),
+									'color' => array(
+										'type' => 'string',
+									),
+								),
+							),
+							'readonly'    => true,
+						),
+						'editor-font-sizes'         => array(
+							'description' => __( 'Custom font sizes if defined by the theme.' ),
+							'type'        => array( 'array', 'bool' ),
+							'items'       => array(
+								'type'       => 'object',
+								'properties' => array(
+									'name' => array(
+										'type' => 'string',
+									),
+									'size' => array(
+										'type' => 'number',
+									),
+									'slug' => array(
+										'type' => 'string',
+									),
+								),
+							),
+							'readonly'    => true,
+						),
+						'editor-styles'             => array(
+							'description' => __( 'Whether theme opts in to the editor styles CSS wrapper.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'formats'                   => array(
 							'description' => __( 'Post formats supported.' ),
 							'type'        => 'array',
+							'items'       => array(
+								'type' => 'string',
+							),
+							'readonly'    => true,
+						),
+						'html5'                     => array(
+							'description' => __( 'Allows use of html5 markup for search forms, comment forms, comment lists, gallery, and caption.' ),
+							'type'        => array( 'array', 'bool' ),
+							'items'       => array(
+								'type' => 'string',
+								'enum' => array(
+									'search-form',
+									'comment-form',
+									'comment-list',
+									'gallery',
+									'caption',
+									'script',
+									'style',
+								),
+							),
 							'readonly'    => true,
 						),
-						'post-thumbnails'   => array(
+						'post-thumbnails'           => array(
 							'description' => __( 'Whether the theme supports post thumbnails.' ),
 							'type'        => array( 'array', 'bool' ),
+							'items'       => array(
+								'type' => 'string',
+							),
 							'readonly'    => true,
 						),
-						'responsive-embeds' => array(
+						'responsive-embeds'         => array(
 							'description' => __( 'Whether the theme supports responsive embedded content.' ),
 							'type'        => 'bool',
 							'readonly'    => true,
 						),
+						'title-tag'                 => array(
+							'description' => __( 'Whether the theme can manage the document title tag.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
+						'wp-block-styles'           => array(
+							'description' => __( 'Whether theme opts in to default WordPress block styles for viewing.' ),
+							'type'        => 'bool',
+							'readonly'    => true,
+						),
 					),
 				),
 			),
diff --git a/tests/phpunit/tests/rest-api/rest-themes-controller.php b/tests/phpunit/tests/rest-api/rest-themes-controller.php
index 520dbed9d0..076b2beacd 100644
--- a/tests/phpunit/tests/rest-api/rest-themes-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-themes-controller.php
@@ -188,11 +188,458 @@ class WP_Test_REST_Themes_Controller extends WP_Test_REST_Controller_Testcase {
 		$properties = $data['schema']['properties'];
 		$this->assertEquals( 1, count( $properties ) );
 		$this->assertArrayHasKey( 'theme_supports', $properties );
-
-		$this->assertEquals( 3, count( $properties['theme_supports']['properties'] ) );
+		$this->assertEquals( 17, count( $properties['theme_supports']['properties'] ) );
+		$this->assertArrayHasKey( 'align-wide', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'automatic-feed-links', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'custom-header', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'custom-logo', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'customize-selective-refresh-widgets', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'title-tag', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'dark-editor-style', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'disable-custom-font-sizes', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'editor-color-palette', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'editor-font-sizes', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'editor-styles', $properties['theme_supports']['properties'] );
 		$this->assertArrayHasKey( 'formats', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'html5', $properties['theme_supports']['properties'] );
 		$this->assertArrayHasKey( 'post-thumbnails', $properties['theme_supports']['properties'] );
 		$this->assertArrayHasKey( 'responsive-embeds', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'title-tag', $properties['theme_supports']['properties'] );
+		$this->assertArrayHasKey( 'wp-block-styles', $properties['theme_supports']['properties'] );
+	}
+
+	/**
+	 * Test when a theme does not disable custom colors.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_disable_custom_colors_false() {
+		remove_theme_support( 'disable-custom-colors' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['disable-custom-colors'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['disable-custom-colors'] );
+	}
+
+	/**
+	 * Test when a theme disables custom colors.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_disable_custom_colors_true() {
+		remove_theme_support( 'disable-custom-colors' );
+		add_theme_support( 'disable-custom-colors' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['disable-custom-colors'] );
+	}
+
+	/**
+	 * Test when a theme does not disable custom font sizes.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_disable_custom_font_sizes_false() {
+		remove_theme_support( 'disable-custom-font-sizes' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['disable-custom-font-sizes'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['disable-custom-font-sizes'] );
+	}
+
+	/**
+	 * Test when a theme disables custom font sizes.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_disable_custom_font_sizes_true() {
+		remove_theme_support( 'disable-custom-font-sizes' );
+		add_theme_support( 'disable-custom-font-sizes' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['disable-custom-font-sizes'] );
+	}
+
+	/**
+	 * Test when a theme doesn't support custom font sizes.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_editor_font_sizes_false() {
+		remove_theme_support( 'editor-font-sizes' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['editor-font-sizes'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['editor-font-sizes'] );
+	}
+
+	/**
+	 * Test when a theme supports custom font sizes.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_editor_font_sizes_array() {
+		remove_theme_support( 'editor-font-sizes' );
+		$tiny = array(
+			'name' => 'Tiny',
+			'size' => 8,
+			'slug' => 'tiny',
+		);
+		add_theme_support( 'editor-font-sizes', array( $tiny ) );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertEquals( array( $tiny ), $result[0]['theme_supports']['editor-font-sizes'] );
+	}
+
+	/**
+	 * Test when a theme doesn't support a custom color palette.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_editor_color_palette_false() {
+		remove_theme_support( 'editor-color-palette' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['editor-color-palette'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['editor-color-palette'] );
+	}
+
+	/**
+	 * Test when a theme supports a custom color palette.
+	 *
+	 * @ticket 48798
+	 */
+	public function test_theme_supports_editor_color_palette_array() {
+		remove_theme_support( 'editor-color-palette' );
+		$wordpress_blue = array(
+			'name'  => 'WordPress Blue',
+			'slug'  => 'wordpress-blue',
+			'color' => '#0073AA',
+		);
+		add_theme_support( 'editor-color-palette', array( $wordpress_blue ) );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertEquals( array( $wordpress_blue ), $result[0]['theme_supports']['editor-color-palette'] );
+	}
+
+	/**
+	 * Test when a theme enables automatic feed links.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_supports_enable_automatic_feed_links() {
+		remove_theme_support( 'automatic-feed-links' );
+		add_theme_support( 'automatic-feed-links' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['automatic-feed-links'] );
+	}
+
+	/**
+	 * Test when a theme does not enable automatic feed links.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_supports_does_not_enable_automatic_feed_links() {
+		remove_theme_support( 'automatic-feed-links' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['automatic-feed-links'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['automatic-feed-links'] );
+	}
+
+	/**
+	 * Test when a theme doesn't support a custom logo.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_does_not_support_custom_logo() {
+		remove_theme_support( 'custom-logo' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['custom-logo'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['custom-logo'] );
+	}
+
+	/**
+	 * Test when a theme supports a custom logo.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_supports_custom_logo() {
+		remove_theme_support( 'custom-logo' );
+		$wordpress_logo = array(
+			'height'      => 100,
+			'width'       => 400,
+			'flex-height' => true,
+			'flex-width'  => true,
+			'header-text' => array( 'site-title', 'site-description' ),
+		);
+		add_theme_support( 'custom-logo', $wordpress_logo );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertEquals( $wordpress_logo, $result[0]['theme_supports']['custom-logo'] );
+	}
+
+	/**
+	 * Test when a theme doesn't support a custom header.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_does_not_support_custom_header() {
+		remove_theme_support( 'custom-header' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['custom-header'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['custom-header'] );
+	}
+
+	/**
+	 * Test when a theme supports a custom header.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_supports_custom_header() {
+		remove_theme_support( 'custom-header' );
+		$wordpress_header = array(
+			'default-image'          => '',
+			'random-default'         => false,
+			'width'                  => 0,
+			'height'                 => 0,
+			'flex-height'            => false,
+			'flex-width'             => false,
+			'default-text-color'     => '',
+			'header-text'            => true,
+			'uploads'                => true,
+			'wp-head-callback'       => '',
+			'admin-head-callback'    => '',
+			'admin-preview-callback' => '',
+			'video'                  => false,
+			'video-active-callback'  => 'is_front_page',
+		);
+		add_theme_support( 'custom-header', $wordpress_header );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertEquals( $wordpress_header, $result[0]['theme_supports']['custom-header'] );
+	}
+
+	/**
+	 * Test when a theme doesn't support html5 markup.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_does_not_support_html5() {
+		remove_theme_support( 'html5' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['html5'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['html5'] );
+	}
+
+	/**
+	 * Test when a theme supports html5 markup.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_supports_html5() {
+		remove_theme_support( 'html5' );
+		$html5 = array(
+			'search-form',
+			'comment-form',
+			'comment-list',
+			'gallery',
+			'caption',
+			'script',
+			'style',
+		);
+		add_theme_support( 'html5', $html5 );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertEquals( $html5, $result[0]['theme_supports']['html5'] );
+	}
+
+	/**
+	 * Test when a theme cannot manage title tag.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_cannot_manage_title_tag() {
+		remove_theme_support( 'title-tag' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['title-tag'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['title-tag'] );
+	}
+
+	/**
+	 * Test when a theme can manage title tag.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_can_manage_title_tag() {
+		global $_wp_theme_features;
+		$_wp_theme_features['title-tag'] = true;
+		$response                        = self::perform_active_theme_request();
+		$result                          = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['title-tag'] );
+	}
+
+	/**
+	 * Test when a theme cannot manage Selective Refresh for Widgets.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_cannot_manage_selective_refresh_for_widgets() {
+		remove_theme_support( 'customize-selective-refresh-widgets' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['customize-selective-refresh-widgets'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['customize-selective-refresh-widgets'] );
+	}
+
+	/**
+	 * Test when a theme can mange Selective Refresh for Widgets.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_can_manage_selective_refresh_for_widgets() {
+		remove_theme_support( 'customize-selective-refresh-widgets' );
+		add_theme_support( 'customize-selective-refresh-widgets' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['customize-selective-refresh-widgets'] );
+	}
+
+	/**
+	 * Test when a theme does not opt in to the default block styles for viewing.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_no_wp_block_styles() {
+		remove_theme_support( 'wp-block-styles' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['wp-block-styles'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['wp-block-styles'] );
+	}
+
+	/**
+	 * Test when a theme opts in to the default block styles for viewing.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_wp_block_styles_optin() {
+		remove_theme_support( 'wp-block-styles' );
+		add_theme_support( 'wp-block-styles' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['wp-block-styles'] );
+	}
+
+	/**
+	 * Test when a theme does not opt in to wide alignment CSS class.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_no_align_wide() {
+		remove_theme_support( 'align-wide' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['align-wide'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['align-wide'] );
+	}
+
+	/**
+	 * Test when a theme opts in to wide alignment CSS class.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_align_wide_optin() {
+		remove_theme_support( 'align-wide' );
+		add_theme_support( 'align-wide' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['align-wide'] );
+	}
+
+	/**
+	 * Test when a theme does not opt in to the editor styles CSS wrapper.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_no_editor_styles() {
+		remove_theme_support( 'editor-styles' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['editor-styles'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['editor-styles'] );
+	}
+
+	/**
+	 * Test when a theme opts in to the editor styles CSS wrapper.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_editor_styles_optin() {
+		remove_theme_support( 'editor-styles' );
+		add_theme_support( 'editor-styles' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['editor-styles'] );
+	}
+
+	/**
+	 * Test when a theme does not opt in to the dark editor style UI.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_no_dark_editor_style() {
+		remove_theme_support( 'dark-editor-style' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( isset( $result[0]['theme_supports']['dark-editor-style'] ) );
+		$this->assertFalse( $result[0]['theme_supports']['dark-editor-style'] );
+	}
+
+	/**
+	 * Test when a theme opts in to the dark editor style UI.
+	 *
+	 * @ticket 49037
+	 */
+	public function test_theme_dark_editor_style_optin() {
+		remove_theme_support( 'dark-editor-style' );
+		add_theme_support( 'dark-editor-style' );
+		$response = self::perform_active_theme_request();
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result[0]['theme_supports'] ) );
+		$this->assertTrue( $result[0]['theme_supports']['dark-editor-style'] );
 	}
 
 	/**
