pass multiple forward backward

paddle/framework/executor_test.cc

@@ -279,8 +279,10 @@ TEST_F(ExecutorTesterRandom, GPU) {
   std::unique_ptr<Executor> executor(new Executor(places));
 
   executor->Run(init_pdesc_, GetGlobalScope(), 0);
-  executor->Run(pdesc_, GetGlobalScope(), 0);
-  std::vector<std::vector<float>> result = GetFetchVariable<float>();
+  for (int batch_id = 0; batch_id < 3; batch_id++) {
+    executor->Run(pdesc_, GetGlobalScope(), 0);
+    std::vector<std::vector<float>> result = GetFetchVariable<float>();
+  }
 }
 
 TEST_F(ExecutorTesterFeedAndFetch, GPU) {