test: Migrate small Cypress tests to Playwright (#18922)

Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>

packages/testing/playwright/pages/DemoPage.ts

@@ -0,0 +1,31 @@
+import { BasePage } from './BasePage';
+
+export class DemoPage extends BasePage {
+	async visitDemoPage(theme?: 'dark' | 'light') {
+		const query = theme ? `?theme=${theme}` : '';
+		await this.page.goto('/workflows/demo' + query);
+		await this.getBody().waitFor({ state: 'visible' });
+		// eslint-disable-next-line playwright/no-networkidle
+		await this.page.waitForLoadState('networkidle');
+		await this.page.evaluate(() => {
+			// @ts-expect-error - this is a custom property added by the demo page
+			window.preventNodeViewBeforeUnload = true;
+		});
+	}
+
+	/**
+	 * Import a workflow into the demo page
+	 * @param workflow - The workflow to import
+	 */
+	async importWorkflow(workflow: object) {
+		const OPEN_WORKFLOW = { command: 'openWorkflow', workflow };
+		await this.page.evaluate((message) => {
+			console.log('Posting message:', JSON.stringify(message));
+			window.postMessage(JSON.stringify(message), '*');
+		}, OPEN_WORKFLOW);
+	}
+
+	getBody() {
+		return this.page.locator('body');
+	}
+}