Fix the tests

Author: amontoison

src/order.jl

@@ -351,7 +351,7 @@ function vertices(
             update_bucket!(db, v; degtype, direction)
         end
     end
-    if direction == :low2high
+    if direction == :high2low
         reverse!(π)
     end
     return π
@@ -410,7 +410,7 @@ function vertices(
         end
         num_visited = 0
     end
-    if direction == :low2high
+    if direction == :high2low
         reverse!(π)
     end
     return π