Migrate to pytest (#111)

* Migrate to pytest

All tests were update to use pytest.

Tests were alse black formatted. Eventually all code
will be black formatted but need to merge some PRs first.

.github/workflows/pcb-tools.yml

@@ -18,9 +18,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
-        python -m pip install --upgrade pip
         pip install -r requirements-dev.txt
     - name: Test with pytest
       run: |
-        pip install pytest
         pytest