TAP testing in Python

[Frédéric Mangano-Tarumi]

In order to write tests in Python, we first need to make one important
choice: the test framework. Our main constraint is the output format,
which should be TAP to run along with the existing scripts.

My favorite candidate is pycotap, which holds in a 157-line
no-dependency module that we could put in our tests directory, pretty
much like we did for `test/sharness.sh`. It is implemented as a producer
for Python’s standard unittest module. https://el-tramo.be/pycotap/

Its main opponent is tappy, a set of tools for working with TAP. It
integrates with unittest, pytest and nose. From the documentation, my
impression is that it expects to be invoked with nose or pytest’s
harness, which would be inconsistent with usual TAP test invocation
consisting of calling scripts directly and relying on the shebang.
https://tappy.readthedocs.io/en/latest/producers.html

More alternatives at
https://tappy.readthedocs.io/en/latest/alternatives.html

Unless we plan to use pytest or nose over unittest, I suggest we use use
pycotap. Except for a couple of lines, tests written with pycotap are
standard unittest tests, which nose and pytest can collect results from
too. If our needs evolve, we could easily upgrade to another framework.