UnitTest Python Mock first call to method, second call go as usual

Question

I am mocking a method. I want to raise an exception on the first call, but on exception, I am calling that method again with different parameters, so I want the second call to be processed normally. What do I need to do?

Code

Try 1

with patch('xblock.runtime.Runtime.construct_xblock_from_class', Mock(side_effect=Exception)):

Try 2

with patch('xblock.runtime.Runtime.construct_xblock_from_class', Mock(side_effect=[Exception, some_method])):

On the second call, some_method is returned as it is, and data is not processed with different parameters.

Answer 1

class Foo(object):
  def Method1(self, arg):
    pass

  def Method2(self, arg):
    if not arg:
      raise
    self.Method1(arg)

  def Method3(self, arg):
    try:
      self.Method2(arg)
    except:
      self.Method2('some default value')

class FooTest(unittest.TestCase):
  def SetUp(self):
    self.helper = Foo()

  def TestFooMethod3(self):
    with mock.patch.object(self.helper, 'Method2', 
                           side_effect=[Exception,self.helper.Method1]
                           ) as mock_object:
      self.helper.Method3('fake_arg')
      mock_object.assert_has_calls([mock.call('fake_arg'),
                                    mock.call('some default value')])