Add the helpers for tests.

test/support/data_case.ex

@@ -25,6 +25,7 @@ defmodule DecentralisedBookIndex.DataCase do
       import Ecto.Query
       import DecentralisedBookIndex.DataCase
       import DecentralisedBookIndex.Generators
+      import DecentralisedBookIndex.Helpers
     end
   end
 

test/support/helpers.ex

@@ -0,0 +1,20 @@
+defmodule DecentralisedBookIndex.Helpers do
+  @moduledoc "Helpers for tests"
+
+  @doc """
+  Rerurn a new map with same keys as in map_with_keys.
+  """
+  def get_submap(map, map_with_keys) when is_map(map_with_keys) do
+    Map.take(map, Map.keys(map_with_keys))
+  end
+
+  def get_submap(map, keys) when is_list(keys) do
+    Map.take(map, keys)
+  end
+
+  def get_submaps(map_list, keys) do
+    Enum.map(map_list, fn map ->
+      get_submap(map, keys)
+    end)
+  end
+end