Add a stress test for creating lots of futures

.github/workflows/ci.yml

@@ -85,3 +85,5 @@ jobs:
       run: sudo apt-get install clang libstdc++-12-dev libgc-dev
     - name: Test
       run: sbt rootNative/test
+    - name: Stress Test with Lower Memory
+      run: env GC_MAXIMUM_HEAP_SIZE=256M sbt 'rootNative/testOnly StressTest'

shared/src/test/scala/Stress.scala

@@ -0,0 +1,23 @@
+import gears.async.{Async, Future, AsyncSupport, uninterruptible}
+import gears.async.AsyncOperations.*
+import gears.async.default.given
+import gears.async.Future.MutableCollector
+import java.util.concurrent.atomic.AtomicInteger
+
+class StressTest extends munit.FunSuite:
+  test("survives a stress test that hammers on creating futures") {
+    val total = 200_000L
+    Seq[Long](1, 2, 4, 16, 1024).foreach: parallelism =>
+      val k = AtomicInteger(0)
+      def compute(using Async) =
+        k.incrementAndGet()
+      Async.blocking:
+        val collector = MutableCollector((1L to parallelism).map(_ => Future { compute })*)
+        var sum = 0L
+        for i <- parallelism + 1 to total do
+          sum += collector.results.read().right.get.await
+          collector += Future { compute }
+        for i <- 1L to parallelism do sum += collector.results.read().right.get.await
+        assertEquals(sum, total * (total + 1) / 2)
+
+  }