Lesson learned from PR #903 (infer dependencies from setup.cfg)

When adding a new file manager (e.g. SetupCFGManager) read to _deps.py's get_project_deps() or get_dep_groups(), the agent correctly updated tests/usethis/test_deps.py but missed tests/usethis/test_init.py, which calls write_simple_requirements_txt() — a function that transitively calls get_project_deps().

This caused 5 CI test failures:

• tests/usethis/test_init.py::TestWriteSimpleRequirementsTxt::* all raised UnexpectedSetupCFGIOError because SetupCFGManager was not opened in the test context.

Root cause

The agent only searched for direct callers of get_project_deps and get_dep_groups in tests, not for transitive callers (functions that call those functions). write_simple_requirements_txt() in _init.py calls get_project_deps() but is tested in a different test file.

Recommendation

When modifying _deps.py to add new file manager reads, the agent should:

1. Search for all functions that transitively call the modified functions (not just direct callers).
2. Run a broader set of tests — at minimum tests/usethis/test_init.py, tests/usethis/test_deps.py, and tests/usethis/_core/test_core_tool.py — not just test_deps.py.

See also the stored memory: "When adding new file manager reads to _deps.py, ALL existing tests calling those functions must also open the corresponding file manager context."