test: add oracle rate limiting load coverage

oracle/tests/rate-limiting.test.ts

@@ -0,0 +1,62 @@
+/**
+ * Load tests for provider rate limiting under concurrent requests.
+ */
+
+import { describe, it, expect } from 'vitest';
+import { BasePriceProvider } from '../src/providers/base-provider.js';
+import type { RawPriceData } from '../src/types/index.js';
+
+class RateLimitTestProvider extends BasePriceProvider {
+  public completionTimes: number[] = [];
+
+  constructor(maxRequests: number, windowMs: number) {
+    super({
+      name: 'rate-limit-test-provider',
+      enabled: true,
+      priority: 1,
+      weight: 1,
+      baseUrl: 'https://mock.api',
+      rateLimit: { maxRequests, windowMs },
+    });
+  }
+
+  async fetchPrice(asset: string): Promise<RawPriceData> {
+    await this.enforceRateLimit();
+    this.completionTimes.push(Date.now());
+    return {
+      asset: asset.toUpperCase(),
+      price: 1,
+      timestamp: Math.floor(Date.now() / 1000),
+      source: this.name,
+    };
+  }
+}
+
+describe('Oracle rate limiting load tests', () => {
+  it('queues concurrent requests above configured rate limit', async () => {
+    const provider = new RateLimitTestProvider(5, 50);
+    const start = Date.now();
+
+    await Promise.all(Array.from({ length: 20 }, () => provider.fetchPrice('XLM')));
+
+    const elapsed = Date.now() - start;
+    expect(provider.completionTimes).toHaveLength(20);
+    // At least one batch must be deferred beyond the initial window.
+    const deferredCount = provider.completionTimes.filter((t) => t - start >= 50).length;
+    expect(deferredCount).toBeGreaterThan(0);
+    expect(elapsed).toBeGreaterThanOrEqual(50);
+  });
+
+  it('does not allow more than maxRequests in the first window', async () => {
+    const maxRequests = 4;
+    const windowMs = 60;
+    const provider = new RateLimitTestProvider(maxRequests, windowMs);
+    const start = Date.now();
+
+    await Promise.all(Array.from({ length: 12 }, () => provider.fetchPrice('XLM')));
+
+    const inFirstWindow = provider.completionTimes.filter((t) => t - start < windowMs).length;
+    expect(inFirstWindow).toBeLessThanOrEqual(maxRequests);
+    expect(provider.completionTimes).toHaveLength(12);
+  });
+});