new_contents: """
  Test unit lookup tables and registry
  
  
  
  
  """
  
  # -----------------------------------------------------------------------------
  # Copyright (c) 2018, yt Development Team.
  #
  # Distributed under the terms of the Modified BSD License.
  #
  # The full license is in the LICENSE file, distributed with this software.
  # -----------------------------------------------------------------------------
  
  import pytest
  
  from unyt.dimensions import length
  from unyt.exceptions import (
      SymbolNotFoundError,
      UnitParseError,
  )
  from unyt.unit_registry import UnitRegistry
  
  
  def test_add_error():
      ureg = UnitRegistry()
  
      with pytest.raises(UnitParseError):
          ureg.add('tayne', 1, length)
      with pytest.raises(UnitParseError):
          ureg.add('tayne', 'blah', length)
      with pytest.raises(UnitParseError):
          ureg.add('tayne', 1.0, length, offset=1)
      with pytest.raises(UnitParseError):
          ureg.add('tayne', 1.0, length, offset='blah')
  
      ureg.add('tayne', 1.1, length)
  
      with pytest.raises(SymbolNotFoundError):
          ureg.remove('tayn')
  
subject: add some unit registry tests