schema_case.ex

defmodule Services.SchemaCase do
  use ExUnit.CaseTemplate

  using(opts) do
    quote bind_quoted: [opts: opts] do
      alias Services.Repo

      import Ecto
      import Ecto.Changeset
      import Ecto.Query
      import Services.SchemaCase

      @schema opts[:schema]
      @struct opts[:struct]
      @valid_attrs  opts[:valid_attributes]
      @invalid_attrs  opts[:invalid_attributes]

      test "changeset with valid attributes" do
        changeset   = @schema.changeset(@struct, @valid_attrs)
        assert changeset.valid?
      end
      
      test "changeset with invalid attributes" do
        changeset = @schema.changeset(@struct, @invalid_attrs)
        refute changeset.valid?
      end
    end
  end
end

user_schema_test.exs

defmodule Services.Schema.User do
  use Services.SchemaCase,
    valid_attributes: %{name: "Freeeeee",
                        gem_version: "1.01"},
    invalid_attributes: %{foo: "buz"},
    schema: Services.Schema.User,
    struct: %Services.Schema.User{}
end