new_contents: from unittest.mock import MagicMock
  import boto.swf.layer2 as swf
  from boto.swf import layer1
  import pytest
  
  from garcon import activity
  from garcon import decider
  
  
  def mock(monkeypatch):
      for base in [swf.Decider, swf.WorkflowType, swf.ActivityType, swf.Domain]:
          monkeypatch.setattr(base, '__init__', MagicMock(return_value=None))
          if base is not swf.Decider:
              monkeypatch.setattr(base, 'register', MagicMock())
  
  
  def test_create_decider(monkeypatch):
      """Create a decider and check the behavior of the registration.
      """
  
      mock(monkeypatch)
      from tests.fixtures.flows import example
  
      d = decider.DeciderWorker(example)
      assert len(d.activities) == 4
      assert d.flow
      assert d.domain
  
      monkeypatch.setattr(decider.DeciderWorker, 'register', MagicMock())
      d = decider.DeciderWorker(example)
      assert d.register.called
  
      monkeypatch.setattr(decider.DeciderWorker, 'register', MagicMock())
      dec = decider.DeciderWorker(example, register=False)
      assert not dec.register.called
  
subject: Add some tests for the decider.