Add new assert helper function for GraphTopologyDeletion tests

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:?}"
         );
     }
 }