Integrate shunit2 for testing

[jeffhung]

Got the idea to fix issue #5 , but I would like to have more complete testing/evaluation for different scenarios. Therefore, we could integrate shunit2 to build the framework to validate the scenarios.

• Select the canonical shunit2 version (there are many variant versions in the wild)
• Integrate into build process
• Implement some test cases to validate the integration

[jeffhung]

The shunit2 version recognized by popular package systems:

System	Canonical shunit2 version	Known Through
Homebrew	https://github.com/kward/shunit2	brew info shunit2
NetBSD 8.1	https://github.com/kward/shunit2	link
CentOS 6	http://code.google.com/p/shunit2	link
Fedora 30	http://code.google.com/p/shunit2	link
Debian 10	http://code.google.com/p/shunit2	link
Ubuntu 19.10	http://code.google.com/p/shunit2	link

The kward/shunit2 version is very different from the google code version, according to the folder structure.

We shall also consider whether or not the JUnit XML patch could be applied. See: https://code.google.com/archive/p/shunit2/issues/16

[jeffhung]

Noticed the announcement on google code:

NOTICE(2015-06-26): shunit2 has moved to GitHub! http://github.com/kward/shunit2

As the google code version is the previous canonical one, based on the announcement, we shall select the kward/shunit2 version.

[sio]

Have you considered using Python for unit testing?

Since this project already implies being familiar with Python that won't be a new dependency, and unit testing frameworks in Python are very advanced.

I understand that going that way will imply a lot of subprocess calls, but those may be abstracted away with a few helper functions for the most common use cases. Shell scripts for unit tests will be rather tricky to get right in regards of whitespace quoting, regex matching, etc - so Python seems like a worthwhile alternative.

[jeffhung]

As the major use case of python.make is to provision the python environment, I choose to test with shunit2 in order to have no python in prerequisites.

[sio]

Ok, that works too :)

To support my suggestion I was going to add an example of Python-based tests for Makefile before you replied. Now it's too late but here it is anyways (I wrote it for another Makefile project, but the code is easily reusable).