Creating and running tests for a snapcraft plugin

[Joseph Rushton Wakeling]

Hello all,

I have started working on a snapcraft plugin for dub, a build/package manager 
for the D programming language.  The plugin itself is ready (at least in a 
working draft), and now I'm working on the tests.

Is there a simple way to run the tests for a single plugin, rather than the 
whole body of tests?  The snapcraft HACKING.md doesn't offer any advice on this 
point.

I'm not much of a pythonist, so apologies if this is a daft question and the 
answer is as simple as `python3 snapcraft/tests/test_dub.py` (but currently at 
least, even trying that fails with an ImportError, so I assume there's something 
else I have to do).

Thanks & best wishes,

     -- Joe