old_contents: #   Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import unittest
  import numpy as np
  from op_test import OpTest
  
  
  class TestConcatOp(OpTest):
      def setUp(self):
          self.op_type = "concat"
          x0 = np.random.random((2, 1, 4, 5)).astype('float32')
          x1 = np.random.random((2, 2, 4, 5)).astype('float32')
          x2 = np.random.random((2, 3, 4, 5)).astype('float32')
          axis = 1
          self.inputs = {'X': [('x0', x0), ('x1', x1), ('x2', x2)]}
          self.attrs = {'axis': axis}
          self.outputs = {'Out': np.concatenate((x0, x1, x2), axis=axis)}
  
      def test_check_output(self):
          self.check_output()
  
      def test_check_grad(self):
          self.check_grad(['x0'], 'Out')
  
  
  if __name__ == '__main__':
      unittest.main()
  
new_contents: #   Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import unittest
  import numpy as np
  from op_test import OpTest
  
  
  class TestConcatOp(OpTest):
      def setUp(self):
          self.op_type = "concat"
          self.init_test_data()
          self.inputs = {'X': [('x0', self.x0), ('x1', self.x1), ('x2', self.x2)]}
          self.attrs = {'axis': self.axis}
          self.outputs = {
              'Out': np.concatenate(
                  (self.x0, self.x1, self.x2), axis=self.axis)
          }
  
      def test_check_output(self):
          self.check_output()
  
      def test_check_grad(self):
          self.check_grad(['x0'], 'Out')
          self.check_grad(['x1'], 'Out')
          self.check_grad(['x2'], 'Out')
  
      def init_test_data(self):
          self.x0 = np.random.random((2, 1, 4, 5)).astype('float32')
          self.x1 = np.random.random((2, 2, 4, 5)).astype('float32')
          self.x2 = np.random.random((2, 3, 4, 5)).astype('float32')
          self.axis = 1
  
  
  class TestConcatOp2(OpTest):
      def init_test_data(self):
          self.x0 = np.random.random((2, 3, 4, 5)).astype('float32')
          self.x1 = np.random.random((2, 3, 4, 5)).astype('float32')
          self.x2 = np.random.random((2, 3, 4, 5)).astype('float32')
          self.axis = 1
  
  
  if __name__ == '__main__':
      unittest.main()
  
subject: add unit test