Repair unittest and test coverage pipeline

[Bronzila]

This PR adds coverage results to the unittests. An appropriate badge both for passing all tests and the test coverage are added to the README. Moreover the toy test file is deleted and a new file testing the budget exhaustion has been added.

[Neeratyoy]

Could you also, write brief docstrings describing each unit test?
This would then become the template or guide for adding more unit tests.

[Neeratyoy]

Would be nice if all tests pass on this branch, before merging to dev.

Alternatively, you could use the PR to only merge the functionalities that are working and ✅.

[Bronzila]

Would be nice if all tests pass on this branch, before merging to dev.

Alternatively, you could use the PR to only merge the functionalities that are working and ✅.

Currently all Tests pass, the only non-passing actions are pre-commit and docs. I was planning to get these two running on separate branches so that the PRs don't get too large. Would you prefer that I fix them all on one branch?

[Neeratyoy]

I was planning to get these two running on separate branches so that the PRs don't get too large. Would you prefer that I fix them all on one branch?

If it is not too troublesome, we could merge only the unit testing bit and leave these 2 out.
Alternatively, we merge this, and you create a new branch from this merged dev, where a new PR comes in to fix the 2 failing tests for docs and styling.
Whatever you decide as the Occam's razor, especially if fixing the 2 failures is not going to be a time sink.

[Bronzila]

If it is not too troublesome, we could merge only the unit testing bit and leave these 2 out. Alternatively, we merge this, and you create a new branch from this merged dev, where a new PR comes in to fix the 2 failing tests for docs and styling. Whatever you decide as the Occam's razor, especially if fixing the 2 failures is not going to be a time sink.

I would prefer merging this and then creating a new branch with a new PR to fix the docs and styling actions. I don't think it will take too much time to fix these workflows and I think the time is well invested, since we will then have a solid pipeline for clean further developments.