tree can have more than one parent node

test/radiator/outline_test.exs

@@ -372,6 +372,33 @@ defmodule Radiator.OutlineTest do
       assert_level_for_node(tree, nested_node_1, 2)
       assert_level_for_node(tree, nested_node_2, 2)
     end
+
+    test "tree can have more than one parent node", %{
+      parent_node: parent_node
+    } do
+      episode_id = parent_node.episode_id
+
+      other_parent_node =
+        node_fixture(
+          parent_id: nil,
+          prev_id: parent_node.uuid,
+          episode_id: episode_id,
+          content: "also a parent"
+        )
+
+      third_parent_node =
+        node_fixture(
+          parent_id: nil,
+          prev_id: other_parent_node.uuid,
+          episode_id: episode_id,
+          content: "even another root element"
+        )
+
+      {:ok, tree} = Outline.get_node_tree(parent_node.episode_id)
+      assert_level_for_node(tree, parent_node, 0)
+      assert_level_for_node(tree, other_parent_node, 0)
+      assert_level_for_node(tree, third_parent_node, 0)
+    end
   end
 
   defp assert_level_for_node(tree, node, level) do
@@ -381,7 +408,14 @@ defmodule Radiator.OutlineTest do
 
   defp complex_node_fixture(_) do
     episode = PodcastFixtures.episode_fixture()
-    parent_node = node_fixture(episode_id: episode.id, parent_id: nil, prev_id: nil)
+
+    parent_node =
+      node_fixture(
+        episode_id: episode.id,
+        parent_id: nil,
+        prev_id: nil,
+        content: "root of all evil"
+      )
 
     node_1 =
       node_fixture(