diff --git a/src/data/CCGraph.ml b/src/data/CCGraph.ml
index 252a06c5..f7a6eb8a 100644
--- a/src/data/CCGraph.ml
+++ b/src/data/CCGraph.ml
@@ -286,6 +286,21 @@ module Traverse = struct
       } in
       dfs_tag ?eq ~tags ~graph seq
   end
+
+  (*$R
+    let l =
+      Traverse.Event.dfs ~graph:divisors_graph (Sequence.return 345614)
+      |> Sequence.to_list in
+    let expected =
+    [`Enter (345614, 0, []); `Edge (345614, (), 172807, `Forward);
+     `Enter (172807, 1, [(345614, (), 172807)]); `Edge (172807, (), 1, `Forward);
+     `Enter (1, 2, [(172807, (), 1); (345614, (), 172807)]); `Exit 1; `Exit 172807;
+     `Edge (345614, (), 2, `Forward); `Enter (2, 3, [(345614, (), 2)]);
+     `Edge (2, (), 1, `Cross); `Exit 2; `Edge (345614, (), 1, `Cross);
+     `Exit 345614]
+    in
+    assert_equal expected l
+    *)
 end
 
 (** {2 Cycles} *)