Add test

Signed-off-by: marcin mikołajczak <git@mkljczk.pl>

test/support/language_detector_mock.ex

@@ -0,0 +1,18 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule LanguageDetectorMock do
+  alias Pleroma.Language.LanguageDetector.Provider
+
+  @behaviour Provider
+
+  @impl Provider
+  def missing_dependencies, do: []
+
+  @impl Provider
+  def configured?, do: true
+
+  @impl Provider
+  def detect(text), do: "fr"
+end