class RSpec::Mocks::Constant

def self.unmutated(name)
  previously_defined = recursive_const_defined?(name)
rescue NameError
  new(name) do |c|
    c.valid_name = false
  end
else
  new(name) do |const|
    const.previously_defined = previously_defined
    const.original_value = recursive_const_get(name) if previously_defined
  end
end