Port testing to pytest

[davidrudlstorfer]

To simplify the current testing setup and to benefit from additional pytest features the testing suite should be moved to pytest.

[isteinbrecher]

This is for sure a great improvement to the testing of MeshPy! Maybe we can also use this refactoring of the testing to “clean up” the testing structure into more clearly defined subsets of tests. I will think about what could be a good path to go here. However, does not hinder the conversion of the current structure to pytest.

[isteinbrecher]

Just to mention it, we have some "tests" that start with xtest_* that are used to define a base test version that can then be called with different parameters. This construct very likely simply be replaced with pytest parametrize fixtures.

[davidrudlstorfer]

Just to collect the overall ideas for PyTest in an official way:

• Introduce pytest fixtures for globally utilized variables and functions (i.e., reference file path, result comparison functions, ...) (see Add cosserat curve #148 for more details)
• Introduce tagging for tests (https://pypi.org/project/pytest_tagging/) to differentiate between normal tests, performance tests and 4C tests
• Overhaul/update tutorial to Jupyter Notebook and test in separate CI job

[davidrudlstorfer]

#157 introduced the necessary infrastructure and #170 is the issue to port the remaining tests

I'll close this one and open an issue for the tutorials