title: Python mock object instantiation
body: <p>Using Python 2.7, and mock library</p>
  
  <p>How can I test that certain patched object has been initialized with some specific arguments using mock?</p>
  
  <p>Here some sample code and pseudo-code:</p>
  
  <p>unittest.py :</p>
  
  <pre><code>import mock
  @mock.patch('mylib.SomeObject')
  def test_mytest(self, mock_someobject):
    test1 = mock_someobject.return_value
    test1 = method_inside_someobject.side_effect = ['something']
  
    mylib.method_to_test()
  
    # How can I assert that method_to_test instanced SomeObject with certain arguments?
    # I further test things with that method_inside_someobject call, no problems there...
  </code></pre>
  
  <p>mylib.py :</p>
  
  <pre><code>from someobjectmodule import SomeObject
  def method_to_test():
    obj = SomeObject(arg1=val1, arg2=val2, arg3=val3)
    obj.method_inside_someobject()
  </code></pre>
  
  <p>So, how can I test SomeObject was instanced with arg1=val1, arg2=val2, arg3=val3?</p>