chore(python): audit tests

Split the three oversized test files into support modules and topic
files, evaluate the rmdir dir_fd capability once at import, and drop
unused imports.

Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq

tests/test_runtime_removal_error_log.py

@@ -0,0 +1,286 @@
+from __future__ import annotations
+
+import os
+from pathlib import Path
+import subprocess
+import sys
+from typing import Any
+
+import pytest
+
+from elydora.plugins import (
+    _opaque_cleanup,
+    _opaque_removal,
+    _transaction,
+)
+from elydora.plugins._runtime_removal import (
+    commit_runtime_removal,
+    prepare_runtime_removal,
+)
+from runtime_removal_support import (
+    AGENT_ID,
+    AGENT_NAME,
+    prepare_runtime,
+    stream_digest,
+    write_error_log,
+)
+
+
+def test_process_exit_after_opaque_removal_restores_error_log_on_restart(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    expected_digest = write_error_log(error_log, chunks=4)
+    script = """
+import os
+import sys
+from elydora.plugins import _transaction
+from elydora.plugins._runtime_removal import prepare_runtime_removal, commit_runtime_removal
+
+agent_id, agent_name = sys.argv[1:]
+plan = prepare_runtime_removal(agent_id, agent_name)
+assert plan is not None
+_transaction._commit = lambda staged: os._exit(78)
+commit_runtime_removal(plan)
+"""
+    environment = os.environ.copy()
+    environment["HOME"] = os.environ["HOME"]
+    environment["USERPROFILE"] = os.environ["USERPROFILE"]
+
+    completed = subprocess.run(
+        [sys.executable, "-c", script, AGENT_ID, AGENT_NAME],
+        cwd=Path(__file__).resolve().parents[1],
+        env=environment,
+        check=False,
+    )
+
+    assert completed.returncode == 78
+    assert not error_log.exists()
+    _transaction.recover_pending_transactions()
+    assert stream_digest(error_log) == expected_digest
+    assert (agent / "config.json").is_file()
+    assert list(agent.glob(".*.opaque-rollback")) == []
+
+
+def test_error_log_append_at_capture_boundary_fails_and_preserves_append(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    write_error_log(error_log)
+    appended = b"concurrent append\n"
+    original_capture = _opaque_removal._capture_physical
+
+    def append_then_capture(staged: Any) -> None:
+        with error_log.open("ab") as file:
+            file.write(appended)
+            file.flush()
+            os.fsync(file.fileno())
+        original_capture(staged)
+
+    plan = prepare_runtime_removal(AGENT_ID, AGENT_NAME)
+    assert plan is not None
+    monkeypatch.setattr(
+        _opaque_removal,
+        "_capture_physical",
+        append_then_capture,
+    )
+
+    with pytest.raises(OSError, match="changed at commit boundary"):
+        commit_runtime_removal(plan)
+
+    assert error_log.read_bytes().endswith(appended)
+    assert (agent / "config.json").is_file()
+
+
+def test_error_log_replace_at_capture_boundary_preserves_both_files(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    original_digest = write_error_log(error_log)
+    displaced = agent / "displaced-error.log"
+    replacement = b"concurrent replacement\n"
+    original_capture = _opaque_removal._capture_physical
+
+    def replace_then_capture(staged: Any) -> None:
+        error_log.rename(displaced)
+        error_log.write_bytes(replacement)
+        if os.name != "nt":
+            error_log.chmod(0o600)
+        original_capture(staged)
+
+    plan = prepare_runtime_removal(AGENT_ID, AGENT_NAME)
+    assert plan is not None
+    monkeypatch.setattr(
+        _opaque_removal,
+        "_capture_physical",
+        replace_then_capture,
+    )
+
+    with pytest.raises(OSError, match="changed at commit boundary"):
+        commit_runtime_removal(plan)
+
+    assert error_log.read_bytes() == replacement
+    assert stream_digest(displaced) == original_digest
+    assert (agent / "config.json").is_file()
+
+
+def test_error_log_rollback_destination_collision_preserves_victim(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    original_digest = write_error_log(error_log)
+    victim = b"concurrent opaque rollback destination\n"
+    rollback_path: Path | None = None
+    original_capture = _opaque_removal._capture_physical
+
+    def collide_with_rollback_destination(staged: Any) -> None:
+        nonlocal rollback_path
+        assert staged.rollback_path is not None
+        rollback_path = Path(staged.rollback_path)
+        rollback_path.write_bytes(victim)
+        if os.name != "nt":
+            rollback_path.chmod(0o600)
+        original_capture(staged)
+
+    plan = prepare_runtime_removal(AGENT_ID, AGENT_NAME)
+    assert plan is not None
+    monkeypatch.setattr(
+        _opaque_removal,
+        "_capture_physical",
+        collide_with_rollback_destination,
+    )
+
+    with pytest.raises(OSError, match="exist"):
+        commit_runtime_removal(plan)
+
+    assert rollback_path is not None
+    assert rollback_path.read_bytes() == victim
+    assert stream_digest(error_log) == original_digest
+    assert (agent / "config.json").is_file()
+
+
+def test_error_log_cleanup_boundary_append_is_preserved_and_reported(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    write_error_log(error_log)
+    appended = b"cleanup boundary append\n"
+    original_capture = _opaque_cleanup._capture_cleanup_physical
+
+    def append_then_capture(
+        staged: Any,
+        source_path: str,
+    ) -> None:
+        with Path(source_path).open("ab") as file:
+            file.write(appended)
+            file.flush()
+            os.fsync(file.fileno())
+        original_capture(staged, source_path)
+
+    plan = prepare_runtime_removal(AGENT_ID, AGENT_NAME)
+    assert plan is not None
+    monkeypatch.setattr(
+        _opaque_cleanup,
+        "_capture_cleanup_physical",
+        append_then_capture,
+    )
+
+    with pytest.raises(OSError, match="changed at cleanup boundary"):
+        commit_runtime_removal(plan)
+
+    preserved = list(agent.glob(".error.log.*.opaque-rollback"))
+    assert len(preserved) == 1
+    assert preserved[0].read_bytes().endswith(appended)
+    assert list(agent.glob(".*.elydora-quarantine")) == []
+
+
+def test_error_log_cleanup_replacement_preserves_both_identities(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    original_digest = write_error_log(error_log)
+    replacement = b"concurrent cleanup replacement\n"
+    displaced = agent / "displaced-opaque-rollback"
+    rollback_path: Path | None = None
+    original_capture = _opaque_cleanup._capture_cleanup_physical
+
+    def replace_before_cleanup_capture(staged: Any, source_path: str) -> None:
+        nonlocal rollback_path
+        rollback_path = Path(source_path)
+        rollback_path.rename(displaced)
+        rollback_path.write_bytes(replacement)
+        if os.name != "nt":
+            rollback_path.chmod(0o600)
+        original_capture(staged, source_path)
+
+    plan = prepare_runtime_removal(AGENT_ID, AGENT_NAME)
+    assert plan is not None
+    monkeypatch.setattr(
+        _opaque_cleanup,
+        "_capture_cleanup_physical",
+        replace_before_cleanup_capture,
+    )
+
+    with pytest.raises(OSError, match="changed at cleanup boundary") as raised:
+        commit_runtime_removal(plan)
+
+    assert rollback_path is not None
+    assert f"concurrent data preserved at {rollback_path}" in str(raised.value)
+    assert rollback_path.read_bytes() == replacement
+    assert stream_digest(displaced) == original_digest
+    assert list(agent.glob(".*.elydora-quarantine")) == []
+
+
+@pytest.mark.parametrize("entry_kind", ["directory", "symlink"])
+def test_error_log_rejects_nonphysical_entries_before_runtime_mutation(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+    entry_kind: str,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    original_config = (agent / "config.json").read_bytes()
+    if entry_kind == "directory":
+        error_log.mkdir()
+        (error_log / "marker").write_text("preserve", encoding="utf-8")
+    else:
+        target = tmp_path / "external-error.log"
+        target.write_text("preserve", encoding="utf-8")
+        try:
+            error_log.symlink_to(target)
+        except OSError as error:
+            pytest.skip(f"File symbolic links are unavailable: {error}")
+
+    with pytest.raises(OSError, match="not a physical file"):
+        prepare_runtime_removal(AGENT_ID, AGENT_NAME)
+
+    assert (agent / "config.json").read_bytes() == original_config
+    assert error_log.exists() or error_log.is_symlink()
+
+
+@pytest.mark.skipif(os.name == "nt", reason="POSIX owner-only contract")
+def test_error_log_requires_owner_only_permissions_during_prepare(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    _root, agent = prepare_runtime(monkeypatch, tmp_path)
+    error_log = agent / "error.log"
+    error_log.write_text("historical error\n", encoding="utf-8")
+    error_log.chmod(0o640)
+
+    with pytest.raises(PermissionError, match="accessible only by its owner"):
+        prepare_runtime_removal(AGENT_ID, AGENT_NAME)
+
+    assert error_log.read_text(encoding="utf-8") == "historical error\n"