feat: implement Layer 2 per-file transit, RAM session, mock buffer, and tests (v0.2.0)

tests/test_session.py

@@ -0,0 +1,61 @@
+import pytest
+from upload.backend.session import (
+    create_session, add_file, get_files, file_count,
+    store_result, get_result, store_csv, get_csv,
+    touch, pause_ttl, resume_ttl, request_cancel, get_cancel_event,
+    cleanup, configure, MAX_FILE_BYTES, MAX_SESSION_BYTES
+)
+from upload.backend.session.state import _sessions
+
+
+def test_session_lifecycle():
+    sid = create_session()
+    assert sid in _sessions
+    assert file_count(sid) == 0
+    assert get_files(sid) == []
+
+    # Add file
+    ok = add_file(sid, "doc.txt", b"hello world")
+    assert ok is True
+    assert file_count(sid) == 1
+    files = get_files(sid)
+    assert len(files) == 1
+    assert files[0] == ("doc.txt", b"hello world")
+
+    # Store result and csv
+    assert store_result(sid, b"PK...zip") is True
+    assert get_result(sid) == b"PK...zip"
+    assert store_csv(sid, "col1,col2\nval1,val2") is True
+    assert get_csv(sid) == "col1,col2\nval1,val2"
+
+    # Cancel event
+    ev = get_cancel_event(sid)
+    assert ev is not None
+    assert not ev.is_set()
+    assert request_cancel(sid) is True
+    assert ev.is_set()
+
+    # TTL methods do not raise
+    touch(sid)
+    pause_ttl(sid)
+    resume_ttl(sid)
+
+    # Cleanup
+    cleanup(sid)
+    assert sid not in _sessions
+    assert get_files(sid) is None
+    assert file_count(sid) == 0
+
+
+def test_session_limits():
+    sid = create_session()
+    configure(max_session_bytes=100)
+    try:
+        # Add 60 bytes - ok
+        assert add_file(sid, "f1.bin", b"x" * 60) is True
+        # Add 50 bytes - should fail (60 + 50 > 100)
+        assert add_file(sid, "f2.bin", b"x" * 50) is False
+        assert file_count(sid) == 1
+    finally:
+        configure(max_session_bytes=500 * 1024 * 1024)
+        cleanup(sid)