Add a test and enable GitHub Actions (CI)

[szabgab]

The test uses the default example and the default configuration and compares the results to an earlier set of output.
There is a lot to improve on the tests.

Was created during a session of OSDC

[yewtc]

I'm also on the OSDC course and am trying out reviewing the change.
Clearly there could be much more, but at least it's a start. We could extend to use different OS's and perl versions.

[lordfeck]

thanks for the contribution, a bit of CI to automate testing would be helpful! I'll look at getting some of this integrated, will see if we can get this merged with a new branch on my repo

[szabgab]

Why on a branch? The idea of CI is to run on the code as you develop it.

[lordfeck]

@szabgab Fair point. I was thinking I could improve it by dumping it to a temp directory using ./rsru.pl -o ./tmp and then parsing the HTML and XML output using some CPAN modules. That would make the test fully deterministic.

But this gives me a good start so I'll merge it to master now.

[szabgab]

Thanks for accepting.

In general you'd want to make the tests as simple as possible so they won't add extra complexity.
I'd probably create a few examples in the source code with expected output saved also in git and would make them without a timestamp so I won't need to exclude anythings.

One would also need to fix the test environment to make sure the images are generated the same way and exclude the images in cases where they might be different due to different versions of libgd.