automate tests with example inputs

[chaetognatha]

I have now written a large number of positive and negative test inputs that can be used to simulate correct and incorrect input data.

As validation is getting more complex it would be good to write automated tests that can verify that the validation behaves correctly and output is uniform.

Can be closed when we added pytests that instantiate objects from the class pep2samplesheet and verify that the behavior matches expectations from data/test