single: Mocking; Magic Methods
PHP magic methods which are prefixed with a double underscore, e.g. __set(), pose a particular problem in mocking and unit testing in general. It is strongly recommended that unit tests and mock objects do not directly refer to magic methods. Instead, refer only to the virtual methods and properties these magic methods simulate.
Following this piece of advice will ensure you are testing the real API of classes and also ensures there is no conflict should Mockery override these magic methods, which it will inevitably do in order to support its role in intercepting method calls and properties.