`and_assert_not_called` shouldn't need any behaviour defined beforehand about testslide

[deathowl]

Will do this soon, thanks for the report @Piojo :)

[fornellas]

@Piojo I believe all 3 cases should raise an exception if a call is made:

self.mock_callable(foo, 'bar')
self.mock_callable(foo, 'bar').and_assert_not_called()
self.mock_callable(foo, 'bar').to_return_value(None).and_assert_not_called()

sot "they work equally". Though:

• The exception from self.mock_callable(foo, 'bar') sohuld be generic such as "no behaviour defined for this call".
• And for the others, the exception should be "unexpected call received".
  So... "kinda" the same, though not really :-P

No harm in adding self.mock_callable(foo, 'bar').and_assert_not_called() shortcut though :-D