Test: Add e2e test that ensures that filters can be added after block…

… registration

packages/e2e-tests/plugins/block-api.php

@@ -0,0 +1,26 @@
+<?php
+/**
+ * Plugin Name: Gutenberg Test Block API
+ * Plugin URI: https://github.com/WordPress/gutenberg
+ * Author: Gutenberg Team
+ *
+ * @package gutenberg-test-block-api
+ */
+
+/**
+ * Registers a custom script for the plugin.
+ */
+function enqueue_block_api_plugin_script() {
+	wp_enqueue_script(
+		'gutenberg-test-block-api',
+		plugins_url( 'block-api/index.js', __FILE__ ),
+		array(
+			'wp-blocks',
+			'wp-hooks',
+		),
+		filemtime( plugin_dir_path( __FILE__ ) . 'block-api/index.js' ),
+		true
+	);
+}
+
+add_action( 'init', 'enqueue_block_api_plugin_script' );

packages/e2e-tests/plugins/block-api/index.js

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+( function () {
+	const { registerBlockType } = wp.blocks;
+	const { addFilter } = wp.hooks;
+
+	registerBlockType( 'e2e-tests/hello-world', {
+		title: 'Hello World',
+		description: 'Hello World test block.',
+		category: 'widgets',
+		edit() {
+			return 'Hello Editor!';
+		},
+		save() {
+			return 'Hello Frontend!';
+		},
+	} );
+
+	addFilter(
+		'blocks.registerBlockType',
+		'e2e-tests/hello-world/filter-added-after-registration',
+		( blockType, name ) => {
+			if ( name === 'e2e-tests/hello-world' ) {
+				return {
+					...blockType,
+					title: 'Filtered Hello World',
+				};
+			}
+
+			return blockType;
+		}
+	);
+} )();

packages/e2e-tests/specs/editor/plugins/block-api.test.js

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+/**
+ * WordPress dependencies
+ */
+import {
+	activatePlugin,
+	createNewPost,
+	deactivatePlugin,
+	insertBlock,
+} from '@wordpress/e2e-test-utils';
+
+describe( 'Using Block API', () => {
+	beforeAll( async () => {
+		await activatePlugin( 'gutenberg-test-block-api' );
+	} );
+
+	afterAll( async () => {
+		await deactivatePlugin( 'gutenberg-test-block-api' );
+	} );
+
+	beforeEach( async () => {
+		await createNewPost();
+	} );
+
+	test( 'Inserts the filtered hello world block even when filter added after block registration', async () => {
+		await insertBlock( 'Filtered Hello World' );
+
+		const blockContent = await page.$eval(
+			'div[data-type="e2e-tests/hello-world"]',
+			( element ) => element.textContent
+		);
+		expect( blockContent ).toEqual( 'Hello Editor!' );
+	} );
+} );