`npm test` fails to run on Windows (`test/run.sh` is not executed)

This is due to the particulars on Windows where the usual install of git-on-windows has a bash shell, but this is not the default command shell (for obvious reasons as then quite a lot of other unrelated things would fail), so any `npm` *script task* which executes a UNIX shell script should do this by invoking `bash -c ` instead of just invoking ``.

Start with test/run.sh and the npm test script that invokes it; reproduce npm test on Windows and check how the shell script is launched. Done means npm test runs successfully on Windows by invoking test/run.sh through bash, with the relevant test command passing.

Written by the indexing model from the issue text.