Create UnitTest not funcitoning for modify methods returning void

#### Description:

Modify methods returning void act differently then other engine methods, in that the return type is the first argument modified, rather then the return value from the method.

This is not handled by the UnitTest component.

#### Steps to reproduce:

Try create a UnitTest with any modify method with a void return type.

#### Expected behaviour:

For modify method with void return:
For the inputs to be deepcloned before method is called
For the Output on the TestData of the UnitTest to be set to the first argument of the method after it has been run.

#### Test file(s):