Remove tests/ from .gitignore and track the existing test suite:
tests/core/test_db.py — DB schema, migration, CRUD
tests/core/test_cache.py — cache helpers
tests/core/test_config.py — config/path helpers
tests/core/test_concurrency.py — app loop accessor
tests/core/api/test_base.py — Post dataclass, BooruClient
tests/gui/popout/test_state.py — 57 state machine tests
All pure Python, no secrets, no external deps. Uses temp DBs and
synthetic data. Run with: pytest tests/