Migrate 'Comments Form' e2e tests to Playwright (#57337)

* Migrate 'Comments Form' e2e tests to Playwright

* Add comment

* Use getSiteSettings and updateSiteSettings

test/e2e/specs/editor/blocks/post-comments-form.spec.js

@@ -0,0 +1,49 @@
+/**
+ * WordPress dependencies
+ */
+const { test, expect } = require( '@wordpress/e2e-test-utils-playwright' );
+
+test.describe( 'Comments Form', () => {
+	let originalCommentStatus;
+
+	test.beforeAll( async ( { requestUtils } ) => {
+		await requestUtils.activateTheme( 'emptytheme' );
+		await requestUtils.deleteAllTemplates( 'wp_template' );
+	} );
+
+	test.beforeEach( async ( { requestUtils } ) => {
+		const siteSettings = await requestUtils.getSiteSettings();
+		originalCommentStatus = siteSettings.default_comment_status;
+	} );
+
+	test.afterEach( async ( { requestUtils } ) => {
+		await requestUtils.updateSiteSettings( {
+			default_comment_status: originalCommentStatus,
+		} );
+	} );
+
+	test.afterAll( async ( { requestUtils } ) => {
+		await requestUtils.activateTheme( 'twentytwentyone' );
+	} );
+
+	test( 'placeholder displays in the site editor even when comments are closed by default', async ( {
+		admin,
+		editor,
+	} ) => {
+		// Navigate to "Singular" post template
+		await admin.visitSiteEditor( {
+			postId: 'emptytheme//singular',
+			postType: 'wp_template',
+			canvas: 'edit',
+		} );
+
+		// Insert post comments form
+		await editor.insertBlock( { name: 'core/post-comments-form' } );
+
+		// Ensure the placeholder is there
+		const postCommentsFormBlock = editor.canvas.locator(
+			'role=document[name="Block: Comments Form"i]'
+		);
+		await expect( postCommentsFormBlock.locator( 'form' ) ).toBeVisible();
+	} );
+} );