test(utils): stress SleeperThread wake and stop control flow

SleeperThread concurrency paths needed stress coverage around wake/stop races.

I added a subprocess stress test that repeatedly interleaves wake_up() and
stop() and verifies the worker exits cleanly.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

test/utils/sleeper_thread.cpp

@@ -19,24 +19,61 @@ SafeSignal<bool>& prepare_for_sleep() {
 }  // namespace waybar::util
 
 namespace {
+int run_in_subprocess(int (*task)()) {
+  const auto pid = fork();
+  if (pid < 0) {
+    return -1;
+  }
+  if (pid == 0) {
+    alarm(5);
+    _exit(task());
+  }
+
+  int status = -1;
+  if (waitpid(pid, &status, 0) != pid) {
+    return -1;
+  }
+  if (!WIFEXITED(status)) {
+    return -1;
+  }
+  return WEXITSTATUS(status);
+}
+
 int run_reassignment_regression() {
   waybar::util::SleeperThread thread;
   thread = [] { std::this_thread::sleep_for(std::chrono::milliseconds(10)); };
   thread = [] { std::this_thread::sleep_for(std::chrono::milliseconds(1)); };
   return 0;
 }
+
+int run_control_flag_stress() {
+  for (int i = 0; i < 200; ++i) {
+    waybar::util::SleeperThread thread;
+    thread = [&thread] { thread.sleep_for(std::chrono::milliseconds(1)); };
+
+    std::thread waker([&thread] {
+      for (int j = 0; j < 100; ++j) {
+        thread.wake_up();
+        std::this_thread::yield();
+      }
+    });
+
+    std::this_thread::sleep_for(std::chrono::milliseconds(2));
+    thread.stop();
+    waker.join();
+    if (thread.isRunning()) {
+      return 1;
+    }
+  }
+  return 0;
+}
 }  // namespace
 
 TEST_CASE("SleeperThread reassignment does not terminate process", "[util][sleeper_thread]") {
-  const auto pid = fork();
+  REQUIRE(run_in_subprocess(run_reassignment_regression) == 0);
-  REQUIRE(pid >= 0);
+}
-
+
-  if (pid == 0) {
+TEST_CASE("SleeperThread control flags are stable under concurrent wake and stop",
-    _exit(run_reassignment_regression());
+          "[util][sleeper_thread]") {
-  }
+  REQUIRE(run_in_subprocess(run_control_flag_stress) == 0);
-
-  int status = -1;
-  REQUIRE(waitpid(pid, &status, 0) == pid);
-  REQUIRE(WIFEXITED(status));
-  REQUIRE(WEXITSTATUS(status) == 0);
 }