old_contents: import unittest
  
  import six
  
  from cupy.cuda import compiler
  from cupy import testing
  
  
  @testing.gpu
  class TestNvrtcStderr(unittest.TestCase):
  
      def test(self):
          # An error message contains the file name `kern.cu`
          with six.assertRaisesRegex(self, compiler.CompileException, 'kern.cu'):
              compiler.compile_using_nvrtc('a')
  
new_contents: import unittest
  
  import six
  
  from cupy.cuda import compiler
  from cupy import testing
  
  
  @testing.gpu
  class TestNvrtcStderr(unittest.TestCase):
  
      def test(self):
          # An error message contains the file name `kern.cu`
          with six.assertRaisesRegex(self, compiler.CompileException, 'kern.cu'):
              compiler.compile_using_nvrtc('a')
  
  
  class TestIsValidKernelName(unittest.TestCase):
  
      def test_valid(self):
          self.assertTrue(compiler.is_valid_kernel_name('valid_name_1'))
  
      def test_empyt(self):
          self.assertFalse(compiler.is_valid_kernel_name(''))
  
      def test_start_with_digit(self):
          self.assertFalse(compiler.is_valid_kernel_name('0_invalid'))
  
      def test_new_line(self):
          self.assertFalse(compiler.is_valid_kernel_name('invalid\nname'))
  
      def test_symbol(self):
          self.assertFalse(compiler.is_valid_kernel_name('invalid$name'))
  
      def test_space(self):
          self.assertFalse(compiler.is_valid_kernel_name('invalid name'))
  
subject: Add more tests