diff --git a/src/models/append_graph.rs b/src/models/append_graph.rs
index 92adb4d..dda99a1 100644
--- a/src/models/append_graph.rs
+++ b/src/models/append_graph.rs
@@ -262,18 +262,16 @@ mod trait_tests {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::testing::fixtures::MakeTestGraph;
 
     #[test]
     fn incident_vertices_paired_index() {
-        let mut graph = AppendGraph::new();
-        let v1 = graph.add_vertex();
-        let v2 = graph.add_vertex();
-        let e = graph.add_edge(v1, v2);
-        let f = Edge(e.0 + 1);
-        let (u1, u2) = graph.incident_vertices(f);
+        let (graph, [v0, v1], e) = AppendGraph::single_edge();
+        let f = Edge::new(e.index() + 1);
+        let (u0, u1) = graph.incident_vertices(f);
         assert!(
-            (u1 == v1 && u2 == v2) || (u1 == v2 && u2 == v1),
-            "unexpected incident vertices {u1:?} and {u2:?} for edge {f:?}"
+            (u0 == v0 && u1 == v1) || (u0 == v1 && u1 == v0),
+            "unexpected incident vertices {u0:?} and {u1:?} for edge {f:?}"
         );
     }
 }
diff --git a/src/testing/graph_topology_deletion_testing.rs b/src/testing/graph_topology_deletion_testing.rs
index dc1f866..c51b42a 100644
--- a/src/testing/graph_topology_deletion_testing.rs
+++ b/src/testing/graph_topology_deletion_testing.rs
@@ -354,25 +354,7 @@ where
             .iter()
             .filter_map(|x| (x.edge != edges[2].0).then_some(x.edge))
             .collect();
-        assert_eq!(
-            graph.incident_edges(vertices[i]).count(),
-            expected.len(),
-            "unexpected incident edge count for vertex {:?} after delete",
-            vertices[i]
-        );
-        for e in graph.incident_edges(vertices[i]) {
-            let pos = expected.iter().position(|f| *f == e).expect(&format!(
-                "unexpected incident edge {e:?} of vertex {:?} after delete",
-                vertices[i]
-            ));
-            expected.swap_remove(pos);
-        }
-        assert!(
-            expected.is_empty(),
-            "expected incident edges {:?} of vertex {:?} not matched after delete",
-            expected,
-            vertices[i]
-        );
+        assert_incident_edges_after_delete(&graph, vertices[i], &mut expected);
     }
 }
 
@@ -388,25 +370,7 @@ where
             .iter()
             .filter_map(|x| (x.vertex != vertices[2]).then_some(x.edge))
             .collect();
-        assert_eq!(
-            graph.incident_edges(vertices[i]).count(),
-            expected.len(),
-            "unexpected incident edge count for vertex {:?} after delete",
-            vertices[i]
-        );
-        for e in graph.incident_edges(vertices[i]) {
-            let pos = expected.iter().position(|f| *f == e).expect(&format!(
-                "unexpected incident edge {e:?} of vertex {:?} after delete",
-                vertices[i]
-            ));
-            expected.swap_remove(pos);
-        }
-        assert!(
-            expected.is_empty(),
-            "expected incident edges {:?} of vertex {:?} not matched after delete",
-            expected,
-            vertices[i]
-        );
+        assert_incident_edges_after_delete(&graph, vertices[i], &mut expected);
     }
 }
 
@@ -536,3 +500,32 @@ fn assert_vertex_incidence_cursor<G: GraphTopology>(
         v
     );
 }
+
+fn assert_incident_edges_after_delete<G: GraphTopology>(
+    graph: &G,
+    v: G::Vertex,
+    expected: &mut Vec<G::Edge>,
+) where
+    G::Vertex: Debug,
+    G::Edge: Debug,
+{
+    assert_eq!(
+        graph.incident_edges(v).count(),
+        expected.len(),
+        "unexpected incident edge count for vertex {:?} after delete",
+        v
+    );
+    for e in graph.incident_edges(v) {
+        let pos = expected.iter().position(|f| *f == e).expect(&format!(
+            "unexpected incident edge {e:?} of vertex {:?} after delete",
+            v
+        ));
+        expected.swap_remove(pos);
+    }
+    assert!(
+        expected.is_empty(),
+        "expected incident edges {:?} of vertex {:?} not matched after delete",
+        expected,
+        v
+    );
+}