diff --git a/oneflow/core/kernel/boxing_kernel_test.cpp b/oneflow/core/kernel/boxing_kernel_test.cpp
index 55c3f394c5df5a5d09ae0438c5b34ada9c2cc815..fb016e6d3a2bcbcbb37ecb94df0ff4391285700e 100644
--- a/oneflow/core/kernel/boxing_kernel_test.cpp
+++ b/oneflow/core/kernel/boxing_kernel_test.cpp
@@ -5,6 +5,8 @@ namespace oneflow {
 
 namespace test {
 
+namespace {
+
 template<typename FloatingPointType>
 BoxingKernel<DeviceType::kCPU, FloatingPointType>* BuildBoxingKernel(
     int32_t in_num, int32_t out_num, int kernel_name,
@@ -262,6 +264,8 @@ void TestBoxingKernelAddClone() {
   }
 }
 
+}  // namespace
+
 }  // namespace test
 
 TEST(boxingkernel, boxing_add_clone_box) {
diff --git a/oneflow/core/kernel/clone_kernel_test.cpp b/oneflow/core/kernel/clone_kernel_test.cpp
index 97a5adc4c2a5ce66a67b74352a2a52b32656708f..5714688a0eb30dbd773d1744b7e0ef7f7abdf958 100644
--- a/oneflow/core/kernel/clone_kernel_test.cpp
+++ b/oneflow/core/kernel/clone_kernel_test.cpp
@@ -8,6 +8,8 @@ namespace oneflow {
 
 namespace test {
 
+namespace {
+
 template<DeviceType device_type, typename FloatingPointType>
 Kernel* BuildCloneKernel(int out_num) {
   OperatorConf op_conf;
@@ -64,6 +66,8 @@ void TestCloneKernel() {
   KTCommon::CheckResult(BnInOp2BlobPtr, "in_diff", "in_diff_expected");
 }
 
+}  // namespace
+
 }  // namespace test
 
 TEST(CloneKernel, clone_cpu) {
diff --git a/oneflow/core/kernel/copy_hd_kernel_test.cpp b/oneflow/core/kernel/copy_hd_kernel_test.cpp
index aec5ce792393bd6dd33f3dba5c02e360b013dfc4..a567efb53f3bdaaa14206d9f280e18befc0e8916 100644
--- a/oneflow/core/kernel/copy_hd_kernel_test.cpp
+++ b/oneflow/core/kernel/copy_hd_kernel_test.cpp
@@ -6,6 +6,8 @@ namespace oneflow {
 
 namespace test {
 
+namespace {
+
 template<typename FloatingPointType>
 std::function<Blob*(const std::string&)> BuildBnInOp2BlobPtr(
     CopyHdOpConf::Type hd_type) {
@@ -69,6 +71,9 @@ void TestCopyHdKernel(CopyHdOpConf::Type hd_type) {
     KTCommonGpu::CheckResult(BnInOp2BlobPtr, "in", "in_diff");
   }
 }
+
+}  // namespace
+
 }  // namespace test
 
 TEST(CopyHdKernel, copy_d2h) {
diff --git a/oneflow/core/kernel/innerproduct_kernel_test.cpp b/oneflow/core/kernel/innerproduct_kernel_test.cpp
index 1d39e31bca2fbe7f9e111d7b83e9a347cedbe6e1..cf4aefadb4ca5256e7d4a22dffe60f845ae312ab 100644
--- a/oneflow/core/kernel/innerproduct_kernel_test.cpp
+++ b/oneflow/core/kernel/innerproduct_kernel_test.cpp
@@ -7,6 +7,8 @@ namespace oneflow {
 
 namespace test {
 
+namespace {
+
 template<DeviceType device_type, typename FloatingPointType>
 std::function<Blob*(const std::string&)> BuildBnInOp2BlobPtr(
     bool has_bias_term) {
@@ -115,6 +117,8 @@ void TestInnerProductKernel(bool has_bias_term) {
   }
 }
 
+}  // namespace
+
 }  // namespace test
 
 TEST(InnerProductKernel, inner_product_kernel_cpu_with_bias) {
diff --git a/oneflow/core/kernel/model_diff_accumulate_kernel_test.cpp b/oneflow/core/kernel/model_diff_accumulate_kernel_test.cpp
index 55f484f48993efce798fe0ffd1f2e4731f671df4..9d149c5ec5a5f8d1f18df7facdaae77222b281dd 100644
--- a/oneflow/core/kernel/model_diff_accumulate_kernel_test.cpp
+++ b/oneflow/core/kernel/model_diff_accumulate_kernel_test.cpp
@@ -8,6 +8,8 @@ namespace oneflow {
 
 namespace test {
 
+namespace {
+
 template<DeviceType device_type, typename FloatingPointType>
 std::function<Blob*(const std::string&)> BuildBnInOp2BlobPtr() {
   using KTCommon = KernelTestCommon<device_type, FloatingPointType>;
@@ -62,6 +64,9 @@ void TestMdDiffAccKernel() {
 
   KTCommon::CheckResult(BnInOp2BlobPtr, "model_diff_acc", "expected_acc");
 }
+
+}  // namespace
+
 }  // namespace test
 
 TEST(MdDiffAccKernel, model_diff_acc_kernel_cpu) {
diff --git a/oneflow/core/kernel/relu_kernel_test.cpp b/oneflow/core/kernel/relu_kernel_test.cpp
index 07c4818490d538210a8943e9434809366faba8ea..7a4649bb553ae3800971f9a9fbb36eb66f462823 100644
--- a/oneflow/core/kernel/relu_kernel_test.cpp
+++ b/oneflow/core/kernel/relu_kernel_test.cpp
@@ -7,6 +7,8 @@ namespace oneflow {
 
 namespace test {
 
+namespace {
+
 template<DeviceType device_type, typename FloatingPointType>
 std::function<Blob*(const std::string&)> BuildBnInOp2BlobPtr() {
   using KTCommon = KernelTestCommon<device_type, FloatingPointType>;
@@ -59,6 +61,9 @@ void TestReluKernel() {
   KTCommon::CheckResult(BnInOp2BlobPtr, "out", "expected_out");
   KTCommon::CheckResult(BnInOp2BlobPtr, "in_diff", "expected_in_diff");
 }
+
+}  // namespace
+
 }  // namespace test
 
 TEST(ReluKernel, relu_kernel_cpu) {