How to not mark Jenkins job as FAILURE when pytest tests fail
Your attempt does not work because Jenkins runs the shell with the errexit (-e) option enabled and that causes the shell to exit right after the pytest command before it reaches your if statement. There is a one-liner however that will work because it is executed as one statement: https://stackoverflow.com/a/31114992/1070890
So your build step would look like this:
sh 'cd tests && python -m pytest || [[ $? -eq 1 ]]'
My solution was to implement the support myself in pytest-custom-exit-code and create a pull request.
From version 0.3.0 of the plugin I can use pytest --suppress-tests-failed-exit-code to get the desired behavior.