new_contents: import unittest, netCDF4, tempfile, os
  
  file_name = tempfile.NamedTemporaryFile(suffix='.nc', delete=False).name
  cache_size = 10000
  cache_nelems = 100
  cache_preempt = 0.5
  cache_size2 = 20000
  cache_nelems2 = 200
  cache_preempt2 = 1.0 
  
  class RefCountTestCase(unittest.TestCase):
  
      def setUp(self):
          nc = netCDF4.Dataset(file_name, mode='w', format='NETCDF4')
          d = nc.createDimension('fred', 2000)
          # can only change cache size in createVariable (not nelems or preemption)
          # this change lasts only as long as file is open.
          v = nc.createVariable('frank','f',('fred',),chunk_cache=15000)
          size, nelems, preempt = v.get_var_chunk_cache()
          assert(size==15000)
          self.file=file_name
          nc.close()
  
      def tearDown(self):
          # Remove the temporary files
          os.remove(self.file)
  
      def runTest(self):
          """testing methods for accessing and changing chunk cache"""
          # change cache parameters before opening fil.
          netCDF4.set_chunk_cache(cache_size, cache_nelems, cache_preempt)
          nc = netCDF4.Dataset(self.file, mode='r')
          # check to see that chunk cache parameters were changed.
          assert(netCDF4.get_chunk_cache() == (cache_size, cache_nelems, cache_preempt))
          # change cache parameters for variable, check
          nc['frank'].set_var_chunk_cache(cache_size2, cache_nelems2, cache_preempt2)
          assert(nc['frank'].get_var_chunk_cache() == (cache_size2, cache_nelems2, cache_preempt2))
          nc.close()
  
  if __name__ == '__main__':
      unittest.main()
  
subject: add tests for chunk cache getters/setters