Description of the desired feature

Originally posted by @SimonMolinsky in pyOpenSci/software-submission#43 (comment)

• [ ] Automated tests: Tests cover essential functions of the package and a reasonable range of inputs and conditions. All tests pass on the local machine.

Yes, the test coverage is 99% and pyGMT has a description of tests in Contributing Guide. But I have two comments here:

1. For full test coverage you need to install not only pytest but pytest-mpl and sphinx-gallery too. Those information are presented in the documentation here but in different paragraphs. Maybe it is a good idea to rewrite this part of documentation slightly and present list of all additional packages needed for testing?
2. The other problem is more confusing. When I run all tests then I got results with 2/3 of tests passing but there is 1/3 that fail. When I look into the test output I see a text This is expected for new tests. So I run test again and I see the same communicate. It is extremely misleading, especially for contributors - if I create new functionalities and run all tests to check if everything is ok I must manually check each failed test if it has phrase This is expected for new tests. Did I miss something?

Looks like we'll need to include a list of the test dependencies in the contributing documentation rather than hide it in https://github.com/GenericMappingTools/pygmt/blob/main/environment.yml

E.g. make a list like:

• pytest-mpl
• sphinx-gallery
• dvc
• etc

Are you willing to help implement and maintain this feature? Yes/No