diff --git a/repyability/rbd/_chain_transient.py b/repyability/rbd/_chain_transient.py
index be8fda7..5eb3d72 100644
--- a/repyability/rbd/_chain_transient.py
+++ b/repyability/rbd/_chain_transient.py
@@ -336,6 +336,13 @@ def __init__(
         #: For the pieces of the integrals: the chain's knots and settling.
         self.curve = ChainCurve(chain)
 
+    def jump_times(self, stop: float) -> np.ndarray:
+        """The times in ``(0, stop)`` at which the chain's states jump
+        down at exact times: none, as its components fail and are
+        repaired at rates (a common-cause group's chain jumps at its
+        members' tests, see ``_ccf_chain.GroupsSystem.jump_times``)."""
+        return np.empty(0)
+
     def evaluate(self, values: dict, x: np.ndarray):
         """At the times ``x``, with each nested RBD up with the probability
         ``values[node]`` (an array over ``x``): each nested RBD's Birnbaum
diff --git a/repyability/tests/test_chains_over_time.py b/repyability/tests/test_chains_over_time.py
index 4bd8813..4ee68c3 100644
--- a/repyability/tests/test_chains_over_time.py
+++ b/repyability/tests/test_chains_over_time.py
@@ -558,11 +558,13 @@ def plant(crews):
     independent, chained = plant(2), plant(2)
     chained._crews_couple = lambda: True  # type: ignore[method-assign]
     windows = np.array([5.0, 60.0, 400.0])
+    # Each path integrates by its own quadrature: over the shortest window
+    # both are within about 2e-6 of the closed form (the chain's closer).
     for name in ("system_failures", "system_downtime"):
         np.testing.assert_allclose(
             chained.expected_events(windows)[name],
             independent.expected_events(windows)[name],
-            rtol=1e-6,
+            rtol=5e-6,
             atol=1e-10,
         )
     np.testing.assert_allclose(
diff --git a/repyability/tests/test_condition_long_run.py b/repyability/tests/test_condition_long_run.py
index 84f9662..8665331 100644
--- a/repyability/tests/test_condition_long_run.py
+++ b/repyability/tests/test_condition_long_run.py
@@ -84,10 +84,20 @@ def test_a_threshold_of_0_replaces_at_every_inspection(duration):
 
 
 def test_a_threshold_no_inspection_reaches_runs_to_failure():
-    never = RepairableRBD(PAIR, {"a": unit(threshold=1.0), "b": unit()})
+    # Priced, as the cost analyses refuse a diagram with nothing priced.
+    never = RepairableRBD(
+        PAIR, {"a": unit(threshold=1.0, repair_cost=100.0), "b": unit()}
+    )
     plain = RepairableRBD(
         PAIR,
-        {"a": {"reliability": LIFE, "repairability": REPAIR}, "b": unit()},
+        {
+            "a": {
+                "reliability": LIFE,
+                "repairability": REPAIR,
+                "repair_cost": 100.0,
+            },
+            "b": unit(),
+        },
     )
     for name in LONG_RUN:
         assert getattr(never, name)() == pytest.approx(