diff --git a/test/plugs/mapped_identity_to_signature_plug_test.exs b/test/plugs/mapped_identity_to_signature_plug_test.exs
new file mode 100644
index 000000000..9aca534e1
--- /dev/null
+++ b/test/plugs/mapped_identity_to_signature_plug_test.exs
@@ -0,0 +1,59 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2018 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.Plugs.MappedSignatureToIdentityPlugTest do
+  use Pleroma.Web.ConnCase
+  alias Pleroma.Web.Plugs.MappedSignatureToIdentityPlug
+
+  import Tesla.Mock
+  import Plug.Conn
+
+  setup do
+    mock(fn env -> apply(HttpRequestMock, :request, [env]) end)
+    :ok
+  end
+
+  defp set_signature(conn, key_id) do
+    conn
+    |> put_req_header("signature", "keyId=\"#{key_id}\"")
+    |> assign(:valid_signature, true)
+  end
+
+  test "it successfully maps a valid identity with a valid signature" do
+    conn =
+      build_conn(:get, "/doesntmattter")
+      |> set_signature("http://mastodon.example.org/users/admin")
+      |> MappedSignatureToIdentityPlug.call(%{})
+
+    refute is_nil(conn.assigns.mapped_identity)
+  end
+
+  test "it successfully maps a valid identity with a valid signature with payload" do
+    conn =
+      build_conn(:post, "/doesntmattter", %{"actor" => "http://mastodon.example.org/users/admin"})
+      |> set_signature("http://mastodon.example.org/users/admin")
+      |> MappedSignatureToIdentityPlug.call(%{})
+
+    refute is_nil(conn.assigns.mapped_identity)
+  end
+
+  test "it considers a mapped identity to be invalid when it mismatches a payload" do
+    conn =
+      build_conn(:post, "/doesntmattter", %{"actor" => "http://mastodon.example.org/users/admin"})
+      |> set_signature("https://niu.moe/users/rye")
+      |> MappedSignatureToIdentityPlug.call(%{})
+
+    assert %{valid_signature: false} == conn.assigns
+  end
+
+  @tag skip: "known breakage; the testsuite presently depends on it"
+  test "it considers a mapped identity to be invalid when the identity cannot be found" do
+    conn =
+      build_conn(:post, "/doesntmattter", %{"actor" => "http://mastodon.example.org/users/admin"})
+      |> set_signature("http://niu.moe/users/rye")
+      |> MappedSignatureToIdentityPlug.call(%{})
+
+    assert %{valid_signature: false} == conn.assigns
+  end
+end