PublisherTest: Use mox instead of mock.

lib/pleroma/signature.ex

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Signature do
+  @behaviour Pleroma.Signature.API
   @behaviour HTTPSignatures.Adapter
 
   alias Pleroma.EctoType.ActivityPub.ObjectValidators

lib/pleroma/signature/api.ex

@@ -0,0 +1,14 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Signature.API do
+  @moduledoc """
+  Behaviour for signing requests and producing HTTP Date headers.
+
+  This is used to allow tests to replace the signing implementation with Mox.
+  """
+
+  @callback sign(user :: Pleroma.User.t(), headers :: map()) :: String.t()
+  @callback signed_date() :: String.t()
+end

lib/pleroma/web/activity_pub/publisher.ex

@@ -26,6 +26,12 @@ defmodule Pleroma.Web.ActivityPub.Publisher do
   ActivityPub outgoing federation module.
   """
 
+  @signature_impl Application.compile_env(
+                    :pleroma,
+                    [__MODULE__, :signature_impl],
+                    Pleroma.Signature
+                  )
+
   @doc """
   Enqueue publishing a single activity.
   """
@@ -125,10 +131,10 @@ defmodule Pleroma.Web.ActivityPub.Publisher do
 
     digest = "SHA-256=" <> (:crypto.hash(:sha256, json) |> Base.encode64())
 
-    date = Pleroma.Signature.signed_date()
+    date = @signature_impl.signed_date()
 
     signature =
-      Pleroma.Signature.sign(actor, %{
+      @signature_impl.sign(actor, %{
         "(request-target)": "post #{path}",
         host: signature_host(uri),
         "content-length": byte_size(json),