Add test peer and test peer set modules.

Author: potatosalad

apps/merge_raft/src/merge_raft.app.src

@@ -69,4 +69,4 @@
         "GitHub" => "https://github.com/WhatsApp/merge_raft"
     }},
     {pkg_name, "merge_raft"}
-]}.
+]}.

apps/merge_raft_test/rebar.lock

@@ -0,0 +1,4 @@
+[{<<"proper">>,
+  {git,"https://github.com/proper-testing/proper.git",
+       {ref,"db4ac35639e0ce8504ff3f07517dae49412a8674"}},
+  0}].

apps/merge_raft_test/src/merge_raft_test.app.src

@@ -25,6 +25,7 @@
 {application, merge_raft_test, [
     {description, "merge_raft_test: test modules for merge_raft"},
     {vsn, "1.0.0"},
+    {mod, {merge_raft_test_app, []}},
     {modules, []},
     {registered, []},
     %% NOTE: Remember to sync changes to `applications` to

apps/merge_raft_test/src/merge_raft_test.erl

@@ -96,4 +96,4 @@
 %%%=============================================================================
 
 -spec dynamic_cast(term()) -> dynamic().
-dynamic_cast(X) -> X.
+dynamic_cast(X) -> X.

apps/merge_raft_test/src/merge_raft_test_app.erl

@@ -0,0 +1,63 @@
+%%%-----------------------------------------------------------------------------
+%%% %CopyrightBegin%
+%%%
+%%% SPDX-License-Identifier: Apache-2.0
+%%%
+%%% Copyright (c) Meta Platforms, Inc. and affiliates.
+%%% Copyright (c) WhatsApp LLC
+%%%
+%%% Licensed under the Apache License, Version 2.0 (the "License");
+%%% you may not use this file except in compliance with the License.
+%%% You may obtain a copy of the License at
+%%%
+%%%     http://www.apache.org/licenses/LICENSE-2.0
+%%%
+%%% Unless required by applicable law or agreed to in writing, software
+%%% distributed under the License is distributed on an "AS IS" BASIS,
+%%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%%% See the License for the specific language governing permissions and
+%%% limitations under the License.
+%%%
+%%% %CopyrightEnd%
+%%%-----------------------------------------------------------------------------
+%%% % @format
+-module(merge_raft_test_app).
+-moduledoc """
+""".
+-moduledoc #{author => ["Andrew Bennett <[email protected]>"]}.
+-moduledoc #{created => "2025-08-26", modified => "2025-08-26"}.
+-moduledoc #{copyright => "Meta Platforms, Inc. and affiliates."}.
+-compile(warn_missing_spec_all).
+-oncall("whatsapp_clr").
+
+-behaviour(application).
+
+%% application callbacks
+-export([
+    start/2,
+    stop/1
+]).
+
+%%%=============================================================================
+%%% application callbacks
+%%%=============================================================================
+
+-spec start(StartType, StartArgs) -> {ok, Pid} | {ok, Pid, State} | {error, Reason} when
+    StartType :: application:start_type(),
+    StartArgs :: term(),
+    Pid :: pid(),
+    State :: term(),
+    Reason :: term().
+start(_StartType, _StartArgs) ->
+    {ok, SupPid} = merge_raft_test_sup:start_link(),
+    {ok, SupPid}.
+
+-spec stop(State) -> Ignored when
+    State :: term(),
+    Ignored :: term().
+stop(_State) ->
+    ok.
+
+%%%-----------------------------------------------------------------------------
+%%% Internal functions
+%%%-----------------------------------------------------------------------------