Add countermodm test

[leonardt]

David has a nice countermodm test here: https://github.com/David-Durst/aetherling/blob/master/tests/test_up.py#L39

We should add it to our test suite.

[phanrahan]

Those tests look good.

I was hoping to use our new test infrastructure in sim mode soon. Should I convert this now, or wait until we have the new infrastructure in place?

[leonardt]

Sorry, I've been sidetracked by cgra efforts. The latest feature in Fault is the peek/expect interface for writing directed tests using verilator. Raj is working on adding support for that interface to the Python simulator. What infrastructure features were you waiting for? I can put them on high priority. Otherwise, right now I'm working on enabling the EQ operator.

[phanrahan]

I would like to turn on sim in test_mantle.py. I think we need to call the functions with BitVectors (including UIntVector and SIntVector). This requires changes to testvectors.

[phanrahan]

I would also like to know how to simulate stateful elements like registers and counters.