test(RateLimiter): add unit tests for RateLimiter class

Author: aasthakhatri11

lib/rate-limit.test.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect, beforeEach, vi } from 'vitest';
 import { rateLimit } from './rate-limit';
+import { RateLimiter } from './rate-limit';
 
 describe('rateLimit', () => {
   beforeEach(() => {
@@ -60,3 +61,48 @@ describe('rateLimit', () => {
     expect(rateLimit(ip2, 60, 60000).success).toBe(true);
   });
 });
+
+describe('RateLimiter', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+  });
+
+  it('allows requests within the limit', () => {
+    // Each check() within the limit should return true
+    const limiter = new RateLimiter(3, 60000);
+    expect(limiter.check('1.1.1.1')).toBe(true);
+    expect(limiter.check('1.1.1.1')).toBe(true);
+    expect(limiter.check('1.1.1.1')).toBe(true);
+  });
+
+  it('blocks requests after exceeding the limit', () => {
+    // 4th request should be denied when limit is 3
+    const limiter = new RateLimiter(3, 60000);
+    limiter.check('2.2.2.2');
+    limiter.check('2.2.2.2');
+    limiter.check('2.2.2.2');
+    expect(limiter.check('2.2.2.2')).toBe(false);
+  });
+
+  it('tracks multiple IPs independently', () => {
+    // Exhausting one IP's limit should not affect another IP
+    const limiter = new RateLimiter(2, 60000);
+    limiter.check('3.3.3.3');
+    limiter.check('3.3.3.3');
+    expect(limiter.check('3.3.3.3')).toBe(false);
+    expect(limiter.check('4.4.4.4')).toBe(true);
+  });
+
+  it('allows requests again after the window resets', () => {
+    // TTL expiry should clear the count, allowing the IP through again
+    const windowMs = 60000;
+    const limiter = new RateLimiter(2, windowMs);
+    limiter.check('5.5.5.5');
+    limiter.check('5.5.5.5');
+    expect(limiter.check('5.5.5.5')).toBe(false);
+
+    vi.advanceTimersByTime(windowMs + 1);
+
+    expect(limiter.check('5.5.5.5')).toBe(true);
+  });
+});