How can I test MuxN module?

[TDppy]

I want to test MuxN module,and I use "run --hw true --moduleName MuxN --harnessName MuxNTest" in sbt shell , but it report error :
[error] Chisel.ChiselException: NullPointer class Chisel.UInt:name gen
[error] at OpenSoC.OpenSoC$.main(main.scala:151)
....

I don't know how to fix it.

[TDppy]

If anybody have solution or want to talk about this project,please be free to contact with me!