Add generic_unix test for scheduler watchdog NIFs

Add test_scheduler_watchdog to the eavmlib test suite covering
status proplist shape, mode toggling, badarg validation, and
heartbeat age population via debug_stall/1.

Signed-off-by: Peter M <petermm@gmail.com>
Amp-Thread-ID: https://ampcode.com/threads/T-019cffb9-55d6-70d2-8382-88fd927bdc77
Co-authored-by: Amp <amp@ampcode.com>

Author: petermm

tests/libs/eavmlib/CMakeLists.txt

@@ -29,6 +29,7 @@ set(ERLANG_MODULES
     test_http_server
     test_mdns
     test_port
+    test_scheduler_watchdog
     test_timer_manager
 )
 

tests/libs/eavmlib/test_scheduler_watchdog.erl

@@ -0,0 +1,99 @@
+%
+% This file is part of AtomVM.
+%
+% Copyright 2026 Peter M <petermm@gmail.com>
+%
+% 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.
+%
+% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
+%
+
+-module(test_scheduler_watchdog).
+
+-export([test/0]).
+
+test() ->
+    ok = test_status_returns_proplist(),
+    ok = test_mode_switch(),
+    ok = test_mode_badarg(),
+    ok = test_stall_updates_ages(),
+    ok.
+
+%% Verify scheduler_watchdog_status/0 returns a well-formed proplist
+test_status_returns_proplist() ->
+    Status = atomvm:scheduler_watchdog_status(),
+    true = is_list(Status),
+    {mode, Mode} = lists:keyfind(mode, 1, Status),
+    true = (Mode =:= restart orelse Mode =:= log_only),
+    {timeout_ms, TimeoutMs} = lists:keyfind(timeout_ms, 1, Status),
+    true = is_integer(TimeoutMs),
+    {poll_interval_ms, PollMs} = lists:keyfind(poll_interval_ms, 1, Status),
+    true = is_integer(PollMs),
+    {active_mask, Mask} = lists:keyfind(active_mask, 1, Status),
+    true = is_integer(Mask),
+    {ages, Ages} = lists:keyfind(ages, 1, Status),
+    true = is_list(Ages),
+    ok.
+
+%% Verify mode can be toggled and status reflects the change
+test_mode_switch() ->
+    ok = atomvm:scheduler_watchdog_mode(log_only),
+    S1 = atomvm:scheduler_watchdog_status(),
+    {mode, log_only} = lists:keyfind(mode, 1, S1),
+
+    ok = atomvm:scheduler_watchdog_mode(restart),
+    S2 = atomvm:scheduler_watchdog_status(),
+    {mode, restart} = lists:keyfind(mode, 1, S2),
+    ok.
+
+%% Verify badarg on invalid mode
+test_mode_badarg() ->
+    ok =
+        try
+            atomvm:scheduler_watchdog_mode(invalid),
+            fail
+        catch
+            error:badarg -> ok
+        end,
+    ok =
+        try
+            atomvm:scheduler_watchdog_mode(42),
+            fail
+        catch
+            error:badarg -> ok
+        end,
+    ok.
+
+%% Stall a scheduler briefly and verify the ages list is populated
+test_stall_updates_ages() ->
+    ok = atomvm:scheduler_watchdog_mode(log_only),
+
+    %% Stall this scheduler for 100ms to generate heartbeat activity
+    ok = atomvm:debug_stall(100),
+
+    Status = atomvm:scheduler_watchdog_status(),
+    {active_mask, Mask} = lists:keyfind(active_mask, 1, Status),
+    true = Mask > 0,
+    {ages, Ages} = lists:keyfind(ages, 1, Status),
+    true = length(Ages) > 0,
+    lists:foreach(
+        fun({SlotId, AgeMs}) ->
+            true = is_integer(SlotId),
+            true = SlotId >= 0,
+            true = is_integer(AgeMs),
+            true = AgeMs >= 0
+        end,
+        Ages
+    ),
+    ok = atomvm:scheduler_watchdog_mode(restart),
+    ok.

tests/libs/eavmlib/tests.erl

@@ -29,6 +29,7 @@ start() ->
         test_http_server,
         test_mdns,
         test_port,
+        test_scheduler_watchdog,
         test_timer_manager,
         test_ahttp_client
     ]).