Does Pants make any guarantees about runtime directory relative to the source tree? Particularly in regards to relative path between some

python_tests

and

resources

?

Yes. It strips the source root, if any. See https://www.pantsbuild.org/docs/resources For tests, it's also often convenient to use files() or relocated_files() instead

resources

are intended to be loaded via pkg_resources mechanisms, using logical names relative to the source root.

files

are just files, relative to the repo root, but you can relocate them (logically) at runtime, as Eric mentioned.