Continue GC code review and cleanup

tests/tools/test_run_destructive_tests.py

@@ -0,0 +1,50 @@
+from pathlib import Path
+
+import pytest
+
+from tools import run_destructive_tests
+
+
+def test_reuses_initial_backup_across_test_attempts(tmp_path: Path) -> None:
+    data_path = tmp_path / "data"
+    backup_root = tmp_path / ".test-backups"
+    data_path.mkdir()
+    backup_root.mkdir()
+    (data_path / "transcription.db").write_text("original", encoding="utf-8")
+
+    initial_backup = run_destructive_tests.create_or_reuse_backup(data_path, backup_root)
+    (data_path / "transcription.db").write_text("overwritten", encoding="utf-8")
+    reused_backup = run_destructive_tests.create_or_reuse_backup(data_path, backup_root)
+
+    assert reused_backup == initial_backup
+    assert (reused_backup / "transcription.db").read_text(encoding="utf-8") == "original"
+    assert [path for path in backup_root.iterdir() if path.is_dir()] == [initial_backup]
+
+
+def test_missing_active_backup_stops_instead_of_replacing_it(tmp_path: Path) -> None:
+    data_path = tmp_path / "data"
+    backup_root = tmp_path / ".test-backups"
+    data_path.mkdir()
+    backup_root.mkdir()
+    (data_path / "transcription.db").write_text("post-test", encoding="utf-8")
+    (backup_root / run_destructive_tests.ACTIVE_BACKUP_FILENAME).write_text("data-backup-missing", encoding="utf-8")
+
+    with pytest.raises(FileNotFoundError, match="Active backup is missing"):
+        run_destructive_tests.create_or_reuse_backup(data_path, backup_root)
+
+    assert not any(path.is_dir() for path in backup_root.iterdir())
+
+
+def test_closing_cycle_preserves_backup(tmp_path: Path) -> None:
+    data_path = tmp_path / "data"
+    backup_root = tmp_path / ".test-backups"
+    data_path.mkdir()
+    backup_root.mkdir()
+    (data_path / "transcription.db").write_text("original", encoding="utf-8")
+    backup_path = run_destructive_tests.create_or_reuse_backup(data_path, backup_root)
+
+    closed_backup = run_destructive_tests.close_active_backup_cycle(backup_root)
+
+    assert closed_backup == backup_path
+    assert backup_path.is_dir()
+    assert not (backup_root / run_destructive_tests.ACTIVE_BACKUP_FILENAME).exists()