diff --git a/tests/unit/test_moving_bodies.py b/tests/unit/test_moving_bodies.py
index f90c725..f5b2814 100644
--- a/tests/unit/test_moving_bodies.py
+++ b/tests/unit/test_moving_bodies.py
@@ -94,7 +94,15 @@ def test_refill_donor_sets_nonempty_within_bounds(radius):
 
 pytest.importorskip("pycuda.driver")
 from CelerisLab import simulation as module  # noqa: E402
-from tests.unit.test_simulation_lifecycle import make_simulation  # noqa: E402
+from tests.unit.test_simulation_lifecycle import Owner, make_simulation  # noqa: E402
+
+
+class ClosableOwner(Owner):
+    """Owner double that refuses activation after close, like CudaContext.activate."""
+    def activate(self):
+        if self.is_closed:
+            raise RuntimeError("CUDA context is closed")
+        return super().activate()
 
 
 def moving_simulation(monkeypatch, *, moving=True):
@@ -316,6 +324,7 @@ def test_moving_circle_excluded_from_static_links():
 
 def test_failed_moving_step_marks_simulation_failed(monkeypatch):
     sim = routed_simulation(monkeypatch)
+    sim.ctx = ClosableOwner()
     bid = sim.add_body("circle", (50., 40.), 10., translation=Translation((0., 0., -1., 1.), .1))
     motion = sim.bodies.get(bid).motion
     motion.set_target((0., .2), (0., .05))
@@ -337,5 +346,7 @@ def test_failed_moving_step_marks_simulation_failed(monkeypatch):
     assert sim._failed is not None and sim.bodies is not None and not sim._closed
     sim.close()  # retry outside the activation succeeds
     assert sim._closed and sim._failed is not None
-    with pytest.raises(RuntimeError, match="Simulation failed"):  # no re-entry after close
+    with pytest.raises(RuntimeError, match="CUDA context is closed"):  # no re-entry after close
         sim.run(1)
+    with pytest.raises(RuntimeError, match="unknown"):  # the failed circle stays refused
+        motion.record()
diff --git a/tests/unit/test_state_regressions.py b/tests/unit/test_state_regressions.py
index 2e9f32a..f7b1ff7 100644
--- a/tests/unit/test_state_regressions.py
+++ b/tests/unit/test_state_regressions.py
@@ -294,8 +294,11 @@ def test_passive_overlap_failure_keeps_live_state(device, entry, second_x):
     sim = SimpleNamespace(bodies=bodies, field=field, lbm_cfg=field.cfg,
                           _initialized=entry == "runtime_edit",
                           _assert_allocation_contract=lambda: None,
-                          stream=SimpleNamespace(synchronize=device.synchronize))
-    sim._require_usable = Simulation._require_usable.__get__(sim)
+                          stream=SimpleNamespace(synchronize=device.synchronize),
+                          stepper=SimpleNamespace(blocked=None))
+    for name in ("_require_usable", "_moving_bodies", "_reject_moving_bodies",
+                 "_validate_moving_bodies"):
+        setattr(sim, name, getattr(Simulation, name).__get__(sim))
     with pytest.raises(ValueError, match="active fluid receivers|unique cut-link writers"):
         if entry == "sync":
             bodies.sync_to_gpu(field)