feat: zincrBy 메서드 추가 및 테스트 케이스 작성

src/FastCache.spec.ts

@@ -431,6 +431,27 @@ describe('FastCache', () => {
         expect(values).toHaveLength(0);
       });
     });
+
+    describe('zincrBy', () => {
+      test('값의 score를 증가시키면 증가된 score가 반환된다', async () => {
+        const sortedSet = cache.sortedSet('hello');
+
+        await sortedSet.add(100, 'foo');
+        const newScore1 = await sortedSet.zincrBy('foo', 50);
+        expect(newScore1).toBe(150);
+        const newScore2 = await sortedSet.zincrBy('foo', 25);
+        expect(newScore2).toBe(175);
+      });
+
+      test('새로운 값을 추가할 때도 정상 동작하는지 확인', async () => {
+        const sortedSet = cache.sortedSet('hello');
+        await sortedSet.zincrBy('foo', 10);
+
+        const score = await sortedSet.score('foo');
+
+        expect(score).toBe(10);
+      });
+    });
   });
 
   describe('withCache', () => {

src/FastCache.ts

@@ -47,6 +47,7 @@ export interface SortedSetOperations {
   add(score: number, value: string): Promise<void>;
   addAll(entries: Array<{ score: number; value: string }>): Promise<void>;
   remove(...values: Array<string>): Promise<void>;
+  zincrBy(value: string, increment: number): Promise<number>;
   range({
     start,
     stop,
@@ -237,6 +238,10 @@ export class FastCache {
       remove: async (...values: Array<string>): Promise<void> => {
         await this.client.zrem(key, ...values);
       },
+      zincrBy: async (value: string, increment: number): Promise<number> => {
+        const result = await this.client.zincrby(key, increment, value);
+        return parseFloat(result);
+      },
       range: async ({
         start,
         stop,