Fix test flakiness: use consistent tick counting and ensure placement cache sync

Author: ReubenBond

test/Extensions/Tester.Cosmos/ReminderTests_Cosmos.cs

@@ -297,19 +297,20 @@ public async Task Rem_Azure_GT_Basic()
         // Wait for at least 2 ticks for g2, and g1 should have at least 4 by now
         await WaitForReminderTickCountAsync(g2, DR, 2, ENDWAIT);
 
-        long last1 = await g1.GetCounter(DR);
+        // Use GetReminderTickCount for consistent counting (not GetCounter which uses time-based sequence numbers)
+        int last1 = await g1.GetReminderTickCount(DR);
         Assert.True(last1 >= 4, $"Expected g1 to have at least 4 ticks, got {last1}");
-        long last2 = await g2.GetCounter(DR);
+        int last2 = await g2.GetReminderTickCount(DR);
         Assert.True(last2 >= 2, $"Expected g2 to have at least 2 ticks, got {last2}");
 
         await g1.StopReminder(DR);
         // Wait for g2 to get at least 4 ticks total (2 more periods)
         await WaitForReminderTickCountAsync(g2, DR, 4, ENDWAIT);
         await g2.StopReminder(DR);
 
-        long curr1 = await g1.GetCounter(DR);
+        int curr1 = await g1.GetReminderTickCount(DR);
         Assert.True(curr1 >= last1 && curr1 <= last1 + 1, $"Expected g1 counter to stay near {last1} after stopping, got {curr1}");
-        long curr2 = await g2.GetCounter(DR);
+        int curr2 = await g2.GetReminderTickCount(DR);
         Assert.True(curr2 >= 4, $"Expected g2 to have at least 4 ticks, got {curr2}");
     }
 

test/Extensions/TesterAzureUtils/Reminder/ReminderTests_AzureTable.cs

@@ -299,21 +299,22 @@ public async Task Rem_Azure_GT_Basic()
             // Wait for at least 2 ticks for g2
             await WaitForReminderTickCountAsync(g2, DR, 2, ENDWAIT);
 
-            long last1 = await g1.GetCounter(DR);
+            // Use GetReminderTickCount for consistent counting (not GetCounter which uses time-based sequence numbers)
+            int last1 = await g1.GetReminderTickCount(DR);
             // g1 has been running while g2 was getting its 2 ticks, so g1 should have at least 3
             // (2 initial + roughly 1 more during g2's 2 ticks, given timing variance in real-time tests)
             Assert.True(last1 >= 3, $"Expected g1 to have at least 3 ticks, got {last1}");
-            long last2 = await g2.GetCounter(DR);
+            int last2 = await g2.GetReminderTickCount(DR);
             Assert.True(last2 >= 2, $"Expected g2 to have at least 2 ticks, got {last2}");
 
             await g1.StopReminder(DR);
             // Wait for g2 to get at least 4 ticks total (2 more periods)
             await WaitForReminderTickCountAsync(g2, DR, 4, ENDWAIT);
             await g2.StopReminder(DR);
 
-            long curr1 = await g1.GetCounter(DR);
+            int curr1 = await g1.GetReminderTickCount(DR);
             Assert.True(curr1 >= last1 && curr1 <= last1 + 1, $"Expected g1 counter to stay near {last1} after stopping, got {curr1}");
-            long curr2 = await g2.GetCounter(DR);
+            int curr2 = await g2.GetReminderTickCount(DR);
             Assert.True(curr2 >= 4, $"Expected g2 to have at least 4 ticks, got {curr2}");
         }
 

test/TesterInternal/General/ElasticPlacementTest.cs

@@ -310,6 +310,11 @@ private async Task ElasticityGrainPlacementTest(
             var taintedSilo = this.HostedCluster.StartAdditionalSilo();
             await this.HostedCluster.WaitForLivenessToStabilizeAsync();
 
+            // Ensure all silos have the new silo in their placement statistics cache
+            // before we taint it. Without this, placement directors may not know about
+            // the new silo and fail to find candidates.
+            await ForceStatisticsRefreshOnAllSilos();
+
             const long sampleSize = 10;
 
             var taintedGrain = await GetGrainAtSilo(taintedSilo.SiloAddress);