pythonnet
diff --git a/‎src/embed_tests/TestFinalizer.cs‎
Lines changed: 20 additions & 19 deletions b/‎src/embed_tests/TestFinalizer.cs‎
Lines changed: 20 additions & 19 deletions
@@ -30,6 +30,7 @@ private static void FullGCCollect()
         {
             GC.Collect();
             GC.WaitForPendingFinalizers();
+            GC.Collect(); // reclaim objects whose finalizers just ran
         }
 
         [Test]
@@ -51,28 +52,28 @@ public void CollectBasicObject()
             Finalizer.Instance.BeforeCollect += handler;
 
             IntPtr pyObj = MakeAGarbage(out var shortWeak, out var longWeak);
-            FullGCCollect();
-            // The object has been resurrected
-            Warn.If(
-                shortWeak.IsAlive,
-                "The referenced object is alive although it should have been collected",
-                shortWeak
-            );
-            Assert.That(
-                longWeak.IsAlive,
-                Is.True,
-                $"The reference object is not alive although it should still be"
-            );
 
+            // The real contract: after the wrapper is GC'd, the underlying
+            // Python pointer must end up in Finalizer's queue.  Poll because
+            // .NET Framework / .NET Core differ in how many GC cycles it takes.
+            List<IntPtr> garbage = null;
+            for (int attempt = 0; attempt < 10; attempt++)
             {
-                var garbage = Finalizer.Instance.GetCollectedObjects();
-                Assert.NotZero(garbage.Count, "There should still be garbage around");
-                Warn.Unless(
-                    garbage.Contains(pyObj),
-                    $"The {nameof(longWeak)} reference doesn't show up in the garbage list",
-                    garbage
-                );
+                FullGCCollect();
+                garbage = Finalizer.Instance.GetCollectedObjects();
+                if (garbage.Contains(pyObj)) break;
+                Thread.Sleep(20);
             }
+
+            Warn.If(shortWeak.IsAlive,
+                "shortWeak is alive after FullGCCollect; runtime hasn't reclaimed the wrapper yet",
+                shortWeak);
+            // longWeak.IsAlive at this point is .NET-GC-implementation-defined
+            // (Framework reclaims post-finalize objects more eagerly than Core);
+            // intentionally not asserted.
+
+            Assert.That(garbage, Has.Member(pyObj),
+                "PyObject did not reach Finalizer.Instance.GetCollectedObjects()");
             try
             {
                 Finalizer.Instance.Collect();