test: Add baseline memory test (#19102)

packages/testing/playwright/utils/performance-helper.ts

@@ -29,6 +29,45 @@ export async function getAllPerformanceMetrics(page: Page) {
 	});
 }
 
+/**
+ * Polls the memory metric from Prometheus endpoint and calculates average
+ * @param baseUrl - The base URL of the n8n instance
+ * @param durationMs - How long to poll in milliseconds
+ * @param intervalMs - Interval between polls in milliseconds
+ * @returns Average memory consumption in bytes
+ */
+export async function pollMemoryMetric(
+	baseUrl: string,
+	durationMs: number = 30000,
+	intervalMs: number = 1000,
+): Promise<number> {
+	const samples: number[] = [];
+	const startTime = Date.now();
+
+	while (Date.now() - startTime < durationMs) {
+		try {
+			const response = await fetch(`${baseUrl}/metrics`);
+			const metricsText = await response.text();
+
+			const memoryMatch = metricsText.match(/n8n_process_resident_memory_bytes\s+(\d+(?:\.\d+)?)/);
+			if (memoryMatch) {
+				const memoryBytes = parseFloat(memoryMatch[1]);
+				samples.push(memoryBytes);
+			}
+		} catch (error) {
+			console.error('Error polling memory metric:', error);
+		}
+
+		await new Promise((resolve) => setTimeout(resolve, intervalMs));
+	}
+
+	if (samples.length === 0) {
+		throw new Error('No memory samples collected');
+	}
+
+	return samples.reduce((sum, sample) => sum + sample, 0) / samples.length;
+}
+
 /**
  * Attach a performance metric for collection by the metrics reporter
  * @param testInfo - The Playwright TestInfo object