MPhys testing

[lamkina]

Description

We need to add unit and regression testing for the MPhys layer.

Once we merge PRs #307, #308, and #321 we should create a new PR to add unit and regression tests for MPhys. For the most part, we can mirror the existing ADflow tests and make sure the OpenMDAO derivatives, data, and outputs match with MACH only cases.

[A-CGray]

I guess the main question on this matter is how do we test the parts of the MPhys wrapper that are only used when coupling ADflow to other disciplines? We can add tests that use aerostructural and aeropropulsive scenarios but then the ADflow tests are relying on other codes.

[lamkina]

I think the MPhys tests that live in the ADflow repo should only test the parts of MPhys that interact with ADflow/MACH. The discipline coupling tests can exist in the MPhys repo when we get the dockerized testing workflow set up for all the codes that we couple to MPhys.