Set up unit testing

[njallskarp]

Setup

Based on the research in previous ticket https://github.com/njallskarp/finetune-qa-powerset/issues/15, set up unit testing for the project. This includes the following acceptance criteria

• [x] set up 1-2 unit tests for metrics file
• [x] can run unit tests locally
• [ ] unit tests run on all commits and failed tests block merges

[Eysteinn-Orn]

We can now run unit tests locally on branch #45 and have added 3 very simple unit tests for the metrics file.

Having some getting the tests to run with GHA, some import issues keep occuring

[Eysteinn-Orn]

actually rather, this might be a missing CUDA library files problem