Resolve "complete pytest coverage"

Closes #101 (closed)

Completed automatic test coverage. Several of them concern parts of the code which need external dependencies (pygmo, jax, eryn). In this case, they are skipped if the necessary dependency is not detected in the env.

Also I draw the attention on some code that has been added to the galaxy block. It is a condition to make the block to finish otherwise it is impossible to test it.