[CMake] Configuring CxxTest

[portolan]

Hello,
I setup my first cmake projet, but I have some problems with generating 
my CxxTest suite.
I can easily call up the CxxTest packgage and specify the generator 
using "CXXTEST_PYTHON_TESTGEN_EXECUTABLE" following the instruction of 
the documentation 
(https://cmake.org/cmake/help/v3.0/module/FindCxxTest.html)
.
But how can I specify parameters to the generator? Most notably I use a 
template so I would need to have something along the lines of 
"--template Runner.tpl".

Thanks,

Michele