Problem with `embeds_many`

[dipth]

Given the following schemas:

defmodule MyApp.Games.Game do
  use Ecto.Schema
  import Ecto.Changeset


  schema "games" do
    field :letters, :string
    embeds_many :game_words, MyApp.Games.GameWord
    timestamps()
  end

  @doc false
  def changeset(game, attrs) do
    game
    |> cast(attrs, [:letters])
    |> cast_embed(:game_words, required: true)
    |> validate_required([:letters])
  end
end

defmodule MyApp.Games.GameWord do
  use Ecto.Schema
  import Ecto.Changeset

  embedded_schema do
    field :word_id, :integer
    field :name, :string
    field :score, :integer
  end

  @doc false
  def changeset(game_word, attrs) do
    game_word
    |> cast(attrs, [:word_id, :name, :score])
    |> validate_required([:word_id, :name, :score])
  end
end

I would assume that I could just create the following fixture:

games model: MyApp.Games.Game, repo: MyApp.Repo do
  game1 do
    letters "ABCDEFGHIJKLMNOPQRSTUVWXY"
    game_words [
      %{
        name: "FOO",
        score: 4,
        word_id: 31327
      },
      %{
        name: "BAR",
        score: 5,
        word_id: 32012
      },
      %{
        name: "BAZ",
        score: 8,
        word_id: 32196
      }
    ]
  end
end

But when trying to use that fixture, I get the following error:

     ** (Ecto.InvalidChangesetError) could not perform insert because changeset is invalid.

     Applied changes

         %{
           id: 579810422,
           letters: "ABCDEFGHIJKLMNOPQRSTUVWXY"
         }

     Params

         nil

     Errors

         %{game_words: ["is invalid"]}

     Changeset

         #Ecto.Changeset<
           action: :insert,
           changes: %{
             id: 579810422,
             letters: "ABCDEFGHIJKLMNOPQRSTUVWXY"
           },
           errors: [game_words: "is invalid"],
           data: #MyApp.Games.Game<>,
           valid?: false
         >

     stacktrace:
       (ecto) lib/ecto/repo/schema.ex:128: Ecto.Repo.Schema.insert!/4
       (ecto_fixtures) lib/ecto/fixtures/insertion.ex:6: anonymous fn/4 in EctoFixtures.Insertion.process/2
       (elixir) lib/enum.ex:1899: Enum."-reduce/3-lists^foldl/2-0-"/3
       test/my_app_web/controllers/admin/game_controller_test.exs:3: anonymous fn/2 in MyAppWeb.GameControllerTest.__ex_unit_setup_1/1
       (elixir) lib/enum.ex:1899: Enum."-reduce/3-lists^foldl/2-0-"/3
       test/my_app_web/controllers/admin/game_controller_test.exs:3: MyAppWeb.GameControllerTest.__ex_unit_setup_1/1
       test/my_app_web/controllers/admin/game_controller_test.exs:1: MyAppWeb.GameControllerTest.__ex_unit__/2

Is this library even supposed to support embedded schemas?