diff --git a/app-proto/src/assembly.rs b/app-proto/src/assembly.rs
index 7c6ecaf..bd185c8 100644
--- a/app-proto/src/assembly.rs
+++ b/app-proto/src/assembly.rs
@@ -813,7 +813,7 @@ mod tests {
     fn unindexed_element_test() {
         let _ = create_root(|| {
             let elt = Sphere::default("sphere".to_string(), 0);
-            elt.pose(&mut ConstraintProblem::new(1), &Slab::new());
+            elt.pose(&mut ConstraintProblem::new(1));
         });
     }
     
@@ -821,18 +821,16 @@ mod tests {
     #[should_panic(expected = "Subjects should be indexed before inversive distance regulator writes problem data")]
     fn unindexed_subject_test_inversive_distance() {
         let _ = create_root(|| {
-            let mut elts = Slab::<Rc<dyn Element>>::new();
-            let subjects = [0, 1].map(|k| {
-                elts.insert(
-                    Rc::new(Sphere::default(format!("sphere{k}"), k))
-                )
-            });
-            elts[subjects[0]].set_column_index(0);
+            let subjects = [0, 1].map(
+                |k| Rc::new(Sphere::default(format!("sphere{k}"), k)) as Rc<dyn Element>
+            );
+            subjects[0].set_column_index(0);
             InversiveDistanceRegulator {
                 subjects: subjects,
                 measurement: create_memo(|| 0.0),
-                set_point: create_signal(SpecifiedValue::try_from("0.0".to_string()).unwrap())
-            }.pose(&mut ConstraintProblem::new(2), &elts);
+                set_point: create_signal(SpecifiedValue::try_from("0.0".to_string()).unwrap()),
+                serial: InversiveDistanceRegulator::next_serial()
+            }.pose(&mut ConstraintProblem::new(2));
         });
     }
 }
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