diff --git a/cpp/unittest/server/cache_test.cpp b/cpp/unittest/server/cache_test.cpp
index d45deb7475be5dc8752515c9c7a3bad6f376f80a..df2a869e5c372a7d5b53b4e0c5492058ff286189 100644
--- a/cpp/unittest/server/cache_test.cpp
+++ b/cpp/unittest/server/cache_test.cpp
@@ -58,6 +58,14 @@ public:
 
     }
 
+    engine::VecIndexPtr CopyToGpu(const int64_t &device_id, const engine::Config &cfg) override {
+
+    }
+
+    engine::VecIndexPtr CopyToCpu(const engine::Config &cfg) override {
+
+    }
+
     virtual int64_t Dimension() {
         return dimension_;
     }