test: add characterization tests for core modules

33 tests covering env/io helpers, config parsers, pipeline meta I/O,
worker inbox logic, and FastAPI smoke routes. No gmic/rembg subprocesses.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_worker.py

@@ -0,0 +1,46 @@
+"""Tests for worker inbox helpers."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from app import config
+from app.worker import _file_key, _is_ignored_name, find_new_files, load_processed, save_processed
+
+
+def test_is_ignored_name() -> None:
+    assert _is_ignored_name(".stfolder") is True
+    assert _is_ignored_name(".syncthing.tmp") is True
+    assert _is_ignored_name("photo.jpg") is False
+
+
+def test_find_new_files_skips_processed(data_dir: Path) -> None:
+    photo = config.INBOX_DIR / "party.jpg"
+    photo.write_bytes(b"fake")
+    stat = photo.stat()
+    processed = {
+        _file_key(photo): {
+            "size": stat.st_size,
+            "mtime": stat.st_mtime,
+        }
+    }
+    assert find_new_files(processed) == []
+
+
+def test_find_new_files_picks_supported(data_dir: Path) -> None:
+    (config.INBOX_DIR / "party.jpg").write_bytes(b"fake")
+    (config.INBOX_DIR / "notes.txt").write_text("nope", encoding="utf-8")
+    assert len(find_new_files({})) == 1
+
+
+def test_load_processed_corrupt_warns(data_dir: Path, caplog) -> None:
+    config.PROCESSED_FILE.write_text("{bad", encoding="utf-8")
+    with caplog.at_level("WARNING"):
+        assert load_processed() == {}
+    assert "processed.json unreadable" in caplog.text
+
+
+def test_save_processed_roundtrip(data_dir: Path) -> None:
+    payload = {"incoming/party.jpg": {"size": 1, "mtime": 2}}
+    save_processed(payload)
+    assert load_processed() == payload