Mocking objects in PHP has its limitations and gotchas. Some functionality can’t be mocked or can’t be mocked YET! If you locate such a circumstance, please please (pretty please with sugar on top) create a new issue on GitHub so it can be documented and resolved where possible. Here is a list to note:

  1. Classes containing public __wakeup() methods can be mocked but the mocked __wakeup() method will perform no actions and cannot have expectations set for it. This is necessary since Mockery must serialize and unserialize objects to avoid some __construct() insanity and attempting to mock a __wakeup() method as normal leads to a BadMethodCallException being thrown.
  2. Mockery has two scenarios where real classes are replaced: Instance mocks and alias mocks. Both will generate PHP fatal errors if the real class is loaded, usually via a require or include statement. Only use these two mock types where autoloading is in place and where classes are not explicitly loaded on a per-file basis using require(), require_once(), etc.
  3. Internal PHP classes are not entirely capable of being fully analysed using Reflection. For example, Reflection cannot reveal details of expected parameters to the methods of such internal classes. As a result, there will be problems where a method parameter is defined to accept a value by reference (Mockery cannot detect this condition and will assume a pass by value on scalars and arrays). If references as internal class method parameters are needed, you should use the \Mockery\Configuration::setInternalClassMethodParamMap() method. Note, however that internal class parameter overriding is not available in PHP 8 since incompatible signatures have been reclassified as fatal errors.
  4. Creating a mock implementing a certain interface with incorrect case in the interface name, and then creating a second mock implementing the same interface, but this time with the correct case, will have undefined behavior due to PHP’s class_exists and related functions being case insensitive. Using the ::class keyword in PHP can help you avoid these mistakes.

The gotchas noted above are largely down to PHP’s architecture and are assumed to be unavoidable. But - if you figure out a solution (or a better one than what may exist), let us know!