old_contents: 
  from aneris import io
  
  _defaults = {
      'config': {
          'default_luc_method': 'reduce_ratio_2150_cov',
          'cov_threshold': 20,
      },
  }
  
  
  def test_default_rc():
      exp = _defaults
      obs = io.RunControl()
      for k in exp.keys():
          assert k in obs
          assert exp[k] == obs[k]
  
  
  def test_nondefault_rc():
      rcstr = """
      config:
          cov_threshold: 42
      """
  
      obs = io.RunControl(rcstr)
      exp = _defaults
      exp['config']['cov_threshold'] = 42
      for k in exp.keys():
          assert k in obs
          assert exp[k] == obs[k]
  
new_contents: import pytest
  
  from aneris import io
  
  _defaults = {
      'config': {
          'default_luc_method': 'reduce_ratio_2150_cov',
          'cov_threshold': 20,
      },
  }
  
  
  def test_default_rc():
      exp = _defaults
      obs = io.RunControl()
      for k in exp.keys():
          assert k in obs
          assert exp[k] == obs[k]
  
  
  def test_mutable():
      obs = io.RunControl()
      with pytest.raises(TypeError):
          obs['foo'] = 'bar'
  
  
  def test_nondefault_rc():
      rcstr = """
      config:
          cov_threshold: 42
      """
  
      obs = io.RunControl(rcstr)
      exp = _defaults
      exp['config']['cov_threshold'] = 42
      for k in exp.keys():
          assert k in obs
          assert exp[k] == obs[k]
  
subject: add mutability of rc test