Fix clippy findings and related issues

tests/dfs.rs

@@ -162,11 +162,10 @@ where
     G::Vertex: Debug,
 {
     let (graph, vertices, _, _) = G::standard();
-    for i in 0..10 {
+    for v in vertices {
         assert!(
-            algorithms::dfs_find(&graph, vertices[0], vertices[i]),
-            "vertex {:?} should be reachable from {:?}",
-            vertices[i],
+            algorithms::dfs_find(&graph, vertices[0], v),
+            "vertex {v:?} should be reachable from {:?}",
             vertices[0]
         );
     }
@@ -328,12 +327,8 @@ fn assert_dfs_visited<G: GraphTopology>(
 ) where
     G::Vertex: Debug,
 {
-    for i in 0..10 {
-        assert!(
-            visited[vertices[i]],
-            "vertex {:?} should be visited",
-            vertices[i]
-        );
+    for &v in vertices {
+        assert!(visited[v], "vertex {v:?} should be visited");
     }
 }
 
@@ -349,9 +344,8 @@ fn assert_dfs_predecessors<G: GraphTopology>(
         predecessors[vertices[0]], None,
         "source should have no predecessor"
     );
-    for i in 1..10 {
-        let v = vertices[i];
-        let p = predecessors[v].expect(&format!("vertex {v:?} should have a predecessor"));
+    for &v in vertices.iter().skip(1) {
+        let p = predecessors[v].unwrap_or_else(|| panic!("vertex {v:?} should have a predecessor"));
         assert!(
             visited[p],
             "predecessor {p:?} of vertex {v:?} should be visited"