diff --git a/tests/CodeShellManager.Tests/ThrottledSignalTests.cs b/tests/CodeShellManager.Tests/ThrottledSignalTests.cs
index ce710cc..bf19c51 100644
--- a/tests/CodeShellManager.Tests/ThrottledSignalTests.cs
+++ b/tests/CodeShellManager.Tests/ThrottledSignalTests.cs
@@ -15,6 +15,25 @@ public class ThrottledSignalTests
 {
     private static readonly TimeSpan Delay = TimeSpan.FromMilliseconds(50);
 
+    // Wait for an EVENT, never for a fixed amount of wall clock. These used to sleep 500ms and
+    // then assert, which failed on a loaded CI runner (main, after #160 merged: "Expected: 1,
+    // Actual: 0") — xunit runs test classes in parallel, and a 50ms Task.Delay continuation on
+    // a starved thread pool can land well past 500ms. The deadline below is only a ceiling for
+    // a genuinely broken implementation; a healthy one returns in ~50ms.
+    private static readonly TimeSpan Deadline = TimeSpan.FromSeconds(10);
+
+    // How long to keep watching after the expected count is reached, to catch an EXTRA run.
+    // Several times Delay, so a wrongly scheduled second run would have fired by then.
+    private static readonly TimeSpan Settle = TimeSpan.FromMilliseconds(300);
+
+    private static async Task WaitForRuns(Func<int> runs, int atLeast)
+    {
+        var until = DateTime.UtcNow + Deadline;
+        while (runs() < atLeast && DateTime.UtcNow < until)
+            await Task.Delay(10);
+        Assert.True(runs() >= atLeast, $"expected at least {atLeast} run(s) within {Deadline.TotalSeconds}s, saw {runs()}");
+    }
+
     [Fact]
     public async Task A_burst_of_signals_runs_the_action_once()
     {
@@ -22,9 +41,10 @@ public async Task A_burst_of_signals_runs_the_action_once()
         var signal = new ThrottledSignal(Delay, a => a(), () => Interlocked.Increment(ref runs));
 
         for (int i = 0; i < 1000; i++) signal.Signal();
-        await Task.Delay(500);
+        await WaitForRuns(() => Volatile.Read(ref runs), 1);
+        await Task.Delay(Settle);
 
-        Assert.Equal(1, runs);
+        Assert.Equal(1, Volatile.Read(ref runs));
     }
 
     [Fact]
@@ -34,11 +54,14 @@ public async Task A_signal_after_the_action_ran_schedules_another()
         var signal = new ThrottledSignal(Delay, a => a(), () => Interlocked.Increment(ref runs));
 
         signal.Signal();
-        await Task.Delay(500);
+        // Must wait for the first run itself: signalling again while it is still pending
+        // piggybacks on it, which is the burst case above, not this one.
+        await WaitForRuns(() => Volatile.Read(ref runs), 1);
         signal.Signal();
-        await Task.Delay(500);
+        await WaitForRuns(() => Volatile.Read(ref runs), 2);
+        await Task.Delay(Settle);
 
-        Assert.Equal(2, runs);
+        Assert.Equal(2, Volatile.Read(ref runs));
     }
 
     [Fact]
@@ -54,9 +77,10 @@ public async Task A_signal_during_the_action_is_not_lost()
         });
 
         signal.Signal();
-        await Task.Delay(500);
+        await WaitForRuns(() => Volatile.Read(ref runs), 2);
+        await Task.Delay(Settle);
 
-        Assert.Equal(2, runs);
+        Assert.Equal(2, Volatile.Read(ref runs));
     }
 
     [Fact]