remove the 'using namespace paddle;' in the test files

Author: hedaoyuan

paddle/math/tests/PerfUtils.h

@@ -22,6 +22,7 @@ limitations under the License. */
 #else
 
 #include "paddle/utils/Stat.h"
+using namespace paddle;  // NOLINT
 
 #define EXPRESSION_PERFORMANCE(expression)                             \
   do {                                                                 \

paddle/math/tests/test_Tensor.cu

@@ -16,8 +16,13 @@ limitations under the License. */
 #include "paddle/math/Matrix.h"
 #include "TensorCheck.h"
 
-using namespace paddle;  // NOLINT
-using namespace std;     // NOLINT
+using paddle::Matrix;
+using paddle::CpuMatrix;
+using paddle::GpuMatrix;
+using paddle::CpuVector;
+using paddle::GpuVector;
+using paddle::CpuIVector;
+using paddle::GpuIVector;
 using autotest::TensorCheckEqual;
 using autotest::TensorCheckErr;
 

paddle/math/tests/test_lazyAssign.cu

@@ -18,8 +18,9 @@ limitations under the License. */
 #include "TensorCheck.h"
 #include "PerfUtils.h"
 
-using namespace paddle;  // NOLINT
-using namespace std;     // NOLINT
+using paddle::BaseMatrix;
+using paddle::CpuMatrix;
+using paddle::GpuMatrix;
 using autotest::TensorCheckEqual;
 using autotest::TensorCheckErr;