update test to reproduce problem

test/util/async_task.test.cpp

@@ -206,13 +206,25 @@ TEST(AsyncTask, SequencedScheduler) {
 }
 
 TEST(AsyncTask, MultipleSequencedSchedulers) {
-    std::vector<std::shared_ptr<Scheduler>> shedulers;
+    std::vector<std::shared_ptr<Scheduler>> schedulers;
 
-    for (int i = 0; i < 10; ++i) {
-        std::shared_ptr<Scheduler> scheduler = Scheduler::GetSequenced();
-        EXPECT_TRUE(std::none_of(
-            shedulers.begin(), shedulers.end(), [&scheduler](const auto &item) { return item == scheduler; }));
-        shedulers.emplace_back(std::move(scheduler));
+    // must match the value in the scheduler
+    constexpr std::size_t kSchedulersCount = 10;
+
+    for (std::size_t j = 0; j < kSchedulersCount; ++j) {
+        std::vector<std::shared_ptr<Scheduler>> refs(kSchedulersCount);
+        for (std::size_t i = 0; i < refs.size(); ++i) {
+            refs[i] = Scheduler::GetSequenced();
+        }
+        refs[j].reset();
+
+        // Check that exactly N unique schedulers are produced.
+        // Note that this relies on no other threads requesting schedulers.
+        for (std::size_t i = 0; i < kSchedulersCount; ++i) {
+            auto scheduler = Scheduler::GetSequenced();
+            EXPECT_TRUE(std::ranges::find(schedulers, scheduler) == schedulers.end());
+            schedulers.emplace_back(std::move(scheduler));
+        }
+        EXPECT_EQ(schedulers.front(), Scheduler::GetSequenced());
     }
-    EXPECT_EQ(shedulers.front(), std::shared_ptr<Scheduler>(Scheduler::GetSequenced()));
 }