With the increasing use of models for software development and the emergence of model-driven engineering, it has become important to build accurate and precise models that present certain characteristics. Model transformation testing is a domain that requires generating a large number of models that satisfy coverage properties (cover the code of the transformation or the structure of the metamodel). However, manually building a set of models to test a transformation is a tedious task and having an automatic technique to generate models from a metamodel would be very helpful. We investigate the synthesis of models based on plans. Each plan comprises of a sequence of model synthesis rules (or mutation operators) specified as graph grammar (GG) rules. These mutation operators are primitive GG rules , automatically obtained from any meta-model. Such plans can be evolved by various artificial intelligence techniques to generate useful models for different tasks including model transformation testing.