Added tests for Model::getClone
Removed unnecessary "return by reference" in function signature
Added tests for Model::clearInput
Added tests for Model::clearState
Added tests for Model::setState
Added tests for Model::__call
Update ModelStub to work with parent __call
Added tests for Model::__set
Added tests for Model::__get
Added tests for Model::getHash
Added tests for Model::__construct
Added tests for Model::getInstance
Added tests for Model::getTmpInstance