old_contents: class TestCopyTo(unittest.TestCase):
  
      def test_cpu_to_cpu(self):
          src = numpy.arange(1, 5, dtype=numpy.float32)
          dst = numpy.zeros_like(src)
          cuda.copyto(dst, src)
          numpy.testing.assert_array_equal(dst, src)
  
      @attr.gpu
      def test_cpu_to_gpu(self):
          src = numpy.arange(1, 5, dtype=numpy.float32)
          dst = cuda.cupy.zeros_like(src)
          cuda.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      @attr.gpu
      def test_gpu_to_cpu(self):
          src = cuda.cupy.arange(1, 5, dtype=numpy.float32)
          dst = numpy.zeros_like(src.get())
          cuda.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      @attr.gpu
      def test_gpu_to_gpu(self):
          src = cuda.cupy.arange(1, 5, dtype=numpy.float32)
          dst = cuda.cupy.zeros_like(src)
          cuda.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      @attr.multi_gpu(2)
      def test_gpu_to_another_gpu(self):
          src = cuda.cupy.arange(1, 5, dtype=numpy.float32)
          with cuda.get_device_from_id(1):
              dst = cuda.cupy.zeros_like(src)
          cuda.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      def test_fail_on_invalid_src(self):
          src = None
          dst = numpy.zeros(1)
          with self.assertRaises(TypeError):
              cuda.copyto(dst, src)
  
      def test_fail_on_invalid_dst(self):
          src = numpy.zeros(1)
          dst = None
          with self.assertRaises(TypeError):
              cuda.copyto(dst, src)
  
new_contents: import unittest
  
  import numpy
  
  from chainer import backends
  from chainer.backends import cuda
  from chainer.testing import attr
  
  
  class TestCopyTo(unittest.TestCase):
  
      def test_cpu_to_cpu(self):
          src = numpy.arange(1, 5, dtype=numpy.float32)
          dst = numpy.zeros_like(src)
          backends.copyto(dst, src)
          numpy.testing.assert_array_equal(dst, src)
  
      @attr.gpu
      def test_cpu_to_gpu(self):
          src = numpy.arange(1, 5, dtype=numpy.float32)
          dst = cuda.cupy.zeros_like(src)
          backends.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      @attr.gpu
      def test_gpu_to_cpu(self):
          src = cuda.cupy.arange(1, 5, dtype=numpy.float32)
          dst = numpy.zeros_like(src.get())
          backends.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      @attr.gpu
      def test_gpu_to_gpu(self):
          src = cuda.cupy.arange(1, 5, dtype=numpy.float32)
          dst = cuda.cupy.zeros_like(src)
          backends.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      @attr.multi_gpu(2)
      def test_gpu_to_another_gpu(self):
          src = cuda.cupy.arange(1, 5, dtype=numpy.float32)
          with cuda.get_device_from_id(1):
              dst = cuda.cupy.zeros_like(src)
          backends.copyto(dst, src)
          cuda.cupy.testing.assert_array_equal(dst, src)
  
      def test_fail_on_invalid_src(self):
          src = None
          dst = numpy.zeros(1)
          with self.assertRaises(TypeError):
              backends.copyto(dst, src)
  
      def test_fail_on_invalid_dst(self):
          src = numpy.zeros(1)
          dst = None
          with self.assertRaises(TypeError):
              backends.copyto(dst, src)
  
subject: fix tests to work