feat(tests): add FR1 Python runtime sandbox via sys.addaudithook

tests/test_test_sandbox.py

@@ -1,10 +1,15 @@
-"""Tests for scripts/audit_test_sandbox_violations.py (Phase 2, FR4)."""
+"""Tests for scripts/audit_test_sandbox_violations.py (Phase 2, FR4) and
+the Python audit guard in tests/conftest.py (Phase 3, FR1).
+"""
 from __future__ import annotations
+import os
 import re
 import subprocess
 import sys
 from pathlib import Path
 
+import pytest
+
 
 def test_audit_runs_without_error() -> None:
  """The audit script runs and exits cleanly."""
@@ -84,4 +89,62 @@ def test_audit_subprocess_bad_dir_exits_one() -> None:
   assert result.returncode == 1, f"Expected exit 1, got {result.returncode}"
  finally:
   bad.unlink(missing_ok=True)
-  tmp_dir.rmdir()
+  tmp_dir.rmdir()
+
+
+def test_sandbox_blocks_writes_outside_tests_dir() -> None:
+ """A write to <project_root>/manual_slop.toml raises TEST_SANDBOX_VIOLATION."""
+ bad_path = Path(__file__).resolve().parent.parent / "manual_slop.toml"
+ if bad_path.exists():
+  original = bad_path.read_bytes()
+  existed = True
+ else:
+  existed = False
+  original = b""
+ try:
+  with pytest.raises(RuntimeError, match="TEST_SANDBOX_VIOLATION"):
+   bad_path.write_text("corrupt", encoding="utf-8")
+ finally:
+  if existed:
+   bad_path.write_bytes(original)
+  elif bad_path.exists():
+   bad_path.unlink()
+
+
+def test_sandbox_allows_writes_inside_tests_dir(tmp_path) -> None:
+ """A write to tmp_path (which lives under tests/artifacts/_pytest_tmp) succeeds."""
+ target = tmp_path / "foo.txt"
+ target.write_text("ok", encoding="utf-8")
+ assert target.read_text(encoding="utf-8") == "ok"
+
+
+def test_sandbox_allows_writes_inside_tests_artifacts() -> None:
+ """A write to tests/artifacts/_sandbox_test_allows/foo.txt succeeds."""
+ p = Path("tests/artifacts/_sandbox_test_allows/foo.txt")
+ p.parent.mkdir(parents=True, exist_ok=True)
+ try:
+  p.write_text("ok", encoding="utf-8")
+  assert p.read_text(encoding="utf-8") == "ok"
+ finally:
+  p.unlink(missing_ok=True)
+  if p.parent.exists():
+   p.parent.rmdir()
+
+
+def test_sandbox_does_not_block_reads() -> None:
+ """A read of <project_root>/pyproject.toml succeeds (reads are always allowed)."""
+ pyproject = Path(__file__).resolve().parent.parent / "pyproject.toml"
+ content = pyproject.read_text(encoding="utf-8")
+ assert "[tool.pytest.ini_options]" in content
+
+
+def test_sandbox_allows_pytest_cache_write() -> None:
+ """Writes under .pytest_cache are allowed (pytest internal cache)."""
+ cache_root = Path(__file__).resolve().parent.parent / ".pytest_cache"
+ probe = cache_root / "_sandbox_probe.txt"
+ cache_root.mkdir(parents=True, exist_ok=True)
+ try:
+  probe.write_text("ok", encoding="utf-8")
+  assert probe.read_text(encoding="utf-8") == "ok"
+ finally:
+  probe.unlink(missing_ok=True)