Need unit tests for combined models P(Q)S(Q) etc

[awashington]

The combined model code currently doesn't appear to have any unit tests. We should add some tests in to prevent future regressions.

[butler]

assuming this is part of the combine models that needs to be worked on for the Beta so moving to that work package. Can be moved back (currently SasView Bug Fixing) if it is not appropriate here

[richardh]

Perhaps we could "save analysis" and save I(Q) for a P(Q)S(Q). Then for the test, load analysis, compute and compare a load of the previously saved I(Q).

Any other ideas?

[richardh]

Though this ticket is really about testing P(Q)S(Q) from sasview, as an example of what can go wrong there were initially issues during the Sept 2018 code camp with the calling of multiplicity models from the new qt5 gui.
(a) the number of shells was not being passed properly, (b) there were issues with the initially loaded default parameters continuing to be being sent to sasmodels from the gui instead of the parameters input by the user. Both of these issues were of course resolved, however note that in both cases the models themselves loaded and passed their "unit tests" correctly! Thus I think that we really should have some functionality testing of the whole sasview gui when dealing with more complex models or P(Q)S(Q).