Add more crosscheck tests

tests/conftest.py

@@ -35,3 +35,32 @@ def lab() -> Iterator[LabEnv]:
 def vddk() -> None:
     """Skip VDDK-backed tests when ``libvixDiskLib`` cannot be loaded."""
     require_vddk()
+
+
+def pytest_addoption(parser: pytest.Parser) -> None:
+    """Add ``--runslow`` to opt in to long-running tests."""
+    parser.addoption(
+        "--runslow",
+        action="store_true",
+        default=False,
+        help="run tests marked as slow",
+    )
+
+
+def pytest_configure(config: pytest.Config) -> None:
+    """Register the ``slow`` marker."""
+    config.addinivalue_line(
+        "markers", "slow: long-running tests; enable with --runslow"
+    )
+
+
+def pytest_collection_modifyitems(
+    config: pytest.Config, items: list[pytest.Item]
+) -> None:
+    """Skip ``slow`` tests unless ``--runslow`` was given."""
+    if config.getoption("--runslow"):
+        return
+    skip_slow = pytest.mark.skip(reason="need --runslow to run")
+    for item in items:
+        if "slow" in item.keywords:
+            item.add_marker(skip_slow)