adds new SP compatibility test (currently failing)

while the `compatibility tests` pass, this one is failing (seems CPP SP produces unstable output, to Py.SP fault)

conditions:
* sp.compute() with learn=True
* called directly (I hope I made a mistake in calling the SP..!)

> This PR adds a new unit test, which is failing. The remaining task is to update the codebase to make the test pass. -- Matt