fix backward test case

paddle/framework/backward.cc

@@ -159,7 +159,7 @@ static std::unique_ptr<OperatorBase> BackwardRecursive(
         insert_position.push_back(
             {dup_op.back(),
              OpRegistry::CreateOp(
-                 "add", {{"X", {insert_add_x}}, {"X", {insert_add_y}}},
+                 "sum", {{"X", {insert_add_x}}, {"X", {insert_add_y}}},
                  {{"Out", {insert_add_out}}}, {})});
       }
     }

paddle/framework/backward_test.cc

@@ -133,15 +133,18 @@ class FillZeroOpMaker : public OpProtoAndCheckerMaker {
   }
 };
 
-class AddOpMaker : public OpProtoAndCheckerMaker {
+class SumOpMaker : public framework::OpProtoAndCheckerMaker {
  public:
-  AddOpMaker(OpProto *proto, OpAttrChecker *op_checker)
+  SumOpMaker(framework::OpProto *proto, framework::OpAttrChecker *op_checker)
       : OpProtoAndCheckerMaker(proto, op_checker) {
-    AddInput("X", "x").AsDuplicable();
-    AddOutput("Out", "out");
+    AddInput("X", "the input tensors of sum operator.")
+        .AsDuplicable()
+        .NotInGradient();
+    AddOutput("Out", "the output tensor of sum operator.").NotInGradient();
     AddComment("");
   }
 };
+
 }  // namespace framework
 }  // namespace paddle
 
@@ -154,7 +157,7 @@ REGISTER_OP(mul, f::NOP, f::MulOpMaker, mul_grad, f::NOP);
 REGISTER_OP(sigmoid, f::NOP, f::SigmoidOpMaker, sigmoid_grad, f::NOP);
 REGISTER_OP_WITHOUT_GRADIENT(nograd, f::NOP, f::NoGradOpMaker);
 REGISTER_OP_WITHOUT_GRADIENT(fill_zeros_like, f::NOP, f::FillZeroOpMaker);
-REGISTER_OP(add, f::NOP, f::AddOpMaker, add_grad, f::NOP);
+REGISTER_OP(sum, f::NOP, f::SumOpMaker, sum_grad, f::NOP);
 REGISTER_OP_WITHOUT_GRADIENT(fc, f::FcOp, f::FcOpMaker);
 REGISTER_OP(many_output_op, f::NOP, f::ManyOutputOpMaker, many_output_op_grad,
             f::NOP);
@@ -283,7 +286,7 @@ TEST(Backward, net_shared_weight) {
   ASSERT_TRUE(bwd->IsNetOp());
   auto bwd_net = static_cast<ops::NetOp *>(bwd.get());
   ASSERT_EQ(3UL, bwd_net->ops_.size());
-  ASSERT_EQ("add", bwd_net->ops_[2]->Type());
+  ASSERT_EQ("sum", bwd_net->ops_[2]->Type());
 }
 
 TEST(Backward, op_register_grad_not_for_network) {