test(cache): reject empty cache keys

Author: Divv1524

lib/cache.test.ts

@@ -410,6 +410,15 @@ describe('TTLCache', () => {
       cache.destroy();
     });
 
+    it('rejects an empty string cache key', () => {
+      const cache = new TTLCache<string>();
+
+      expect(() => cache.set('', 'value', 60_000)).toThrow('Cache key cannot be empty');
+      expect(cache.has('')).toBe(false);
+
+      cache.destroy();
+    });
+
     it('handles rapid get/set/delete cycles', () => {
       const cache = new TTLCache<number>();
       for (let i = 0; i < 100; i++) {

lib/cache.ts

@@ -141,6 +141,7 @@ export class TTLCache<T> {
   }
 
   set(key: string, value: T, ttlMs: number): void {
+    if (key === '') throw new Error('Cache key cannot be empty');
     if (ttlMs <= 0) throw new RangeError(`ttlMs must be positive, got ${ttlMs}`);
 
     const maxSize = this.maxSize;