This method will be called by the Create Test Data operation only if CanFillTestData returns true.

This method should at minimum fill all data members with appropriate test data. For single object members, it should either fill them with test data - perhaps by calling FillTestData on them - or set them to null. For contained collections it can leave them empty or create objects.

In cases where contained objects are created, it is up to the developer to create the entire tree under the created objects. The Create Test Data operation recurses down the tree creating objects, but will not recurse below any point at which a single object exists or a collection is not empty.