With this change both C++ and Python write to sys.stdout which resolves
the capture issues noted in #351. Therefore, the related workarounds are
removed.
Use simple asserts and pytest's powerful introspection to make testing
simpler. This merges the old .py/.ref file pairs into simple .py files
where the expected values are right next to the code being tested.
This commit does not touch the C++ part of the code and replicates the
Python tests exactly like the old .ref-file-based approach.
