1 files changed, 20 insertions, 0 deletions
diff --git a/test/mst_test.exs b/test/mst_test.exs
index cf5a898..c1758ad 100644
--- a/test/mst_test.exs
+++ b/test/mst_test.exs
@@ -174,4 +174,24 @@ defmodule ShardTest.MST do
     assert MST.last(mg1, nil, 2000) == all_items
   end
 
+  test "merkle search tree 8: MST.merge callback" do
+    items1 = (for i <- 1..1000, do: i*2+40)
+    items2 = (for i <- 1..1000, do: i*3)
+
+    y = Enum.reduce(items1, %MST{}, fn i, acc -> MST.insert(acc, i) end)
+    z = Enum.reduce(items2, %MST{}, fn i, acc -> MST.insert(acc, i) end)
+
+    {:ok, cb_called} = Agent.start_link fn -> [] end
+
+    cb = fn i, true -> Agent.update(cb_called, fn x -> [i | x] end) end
+    mg = MST.merge(y, z, cb)
+
+    cb_vals = Agent.get cb_called, &(&1)
+    expected = MapSet.difference(MapSet.new(items2), MapSet.new(items1))
+      |> MapSet.to_list
+      |> Enum.sort
+      |> Enum.reverse
+    assert expected == cb_vals
+  end
+
 end