Fix unittest error

paddle/framework/backward_test.cc

@@ -152,8 +152,8 @@ TEST(Backward, simple_op_grad) {
 }
 
 TEST(Backward, net_fc_backward_normal) {
-  std::shared_ptr<f::OperatorBase> fwd =
-      f::OpRegistry::CreateOp("fc", {"X", "w", "b"}, {"out"}, {});
+  std::shared_ptr<f::OperatorBase> fwd = f::OpRegistry::CreateOp(
+      "fc", {"X", "w", "b"}, {"out", "tmp_forward"}, {});
   ASSERT_NE(fwd, nullptr);
   std::shared_ptr<f::OperatorBase> gop = f::Backward(*fwd, {});
   ASSERT_TRUE(gop->IsNetOp());
@@ -175,7 +175,8 @@ TEST(Backward, net_fc_backward_normal) {
 
 TEST(Backward, net_fc_backward_not_have_b) {
   std::shared_ptr<f::OperatorBase> fwd = f::OpRegistry::CreateOp(
-      "fc", {"X", "w", f::OperatorBase::EMPTY_VAR_NAME()}, {"out"}, {});
+      "fc", {"X", "w", f::OperatorBase::EMPTY_VAR_NAME()},
+      {"out", "tmp_forward"}, {});
   ASSERT_NE(fwd, nullptr);
   std::shared_ptr<f::OperatorBase> gop = f::Backward(*fwd, {});
   ASSERT_TRUE(gop->IsNetOp());
@@ -194,9 +195,10 @@ TEST(Backward, net_fc_backward_not_have_b) {
 
 TEST(Backward, net_input_of_network_not_need_grad) {
   f::NetOp net;
-  net.AddOp(f::OpRegistry::CreateOp("fc", {"X", "W1", "b1"}, {"hidden0"}, {}));
-  net.AddOp(
-      f::OpRegistry::CreateOp("fc", {"hidden0", "W2", "b2"}, {"hidden1"}, {}));
+  net.AddOp(f::OpRegistry::CreateOp("fc", {"X", "W1", "b1"},
+                                    {"hidden0", "tmp0"}, {}));
+  net.AddOp(f::OpRegistry::CreateOp("fc", {"hidden0", "W2", "b2"},
+                                    {"hidden1", "tmp1"}, {}));
   net.CompleteAddOp();
   auto bwd = Backward(net, {"X"});  // X@GRAD is not need.
   ASSERT_TRUE(bwd->IsNetOp());