test: add tests for mediaproxy warming policy

test/web/activity_pub/mrf/mediaproxy_warming_policy_test.exs

+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicyTest do
+  use Pleroma.DataCase
+
+  alias Pleroma.HTTP
+  alias Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy
+
+  import Mock
+
+  @message %{
+    "type" => "Create",
+    "object" => %{
+      "type" => "Note",
+      "content" => "content",
+      "attachment" => [
+        %{"url" => [%{"href" => "http://example.com/image.jpg"}]}
+      ]
+    }
+  }
+
+  test "it prefetches media proxy URIs" do
+    with_mock HTTP, get: fn _, _, _ -> {:ok, []} end do
+      MediaProxyWarmingPolicy.filter(@message)
+      assert called(HTTP.get(:_, :_, :_))
+    end
+  end
+
+  test "it does nothing when no attachments are present" do
+    object =
+      @message["object"]
+      |> Map.delete("attachment")
+
+    message =
+      @message
+      |> Map.put("object", object)
+
+    with_mock HTTP, get: fn _, _, _ -> {:ok, []} end do
+      MediaProxyWarmingPolicy.filter(message)
+      refute called(HTTP.get(:_, :_, :_))
+    end
+  end
+end