* added config expect-no-message-default = 3s

* added this config into TestKit setting as ExpectNoMessageDefault property
* in TestKit_Expect, bounded relevant overloads of ExpectNoMsg and ExpectNoMsgAsync to the new config
* updated unit test

src/core/Akka.TestKit.Tests/TestKit_Config_Tests.cs

@@ -19,6 +19,7 @@ public void DefaultValues_should_be_correct()
         {
             TestKitSettings.DefaultTimeout.ShouldBe(TimeSpan.FromSeconds(5));
             TestKitSettings.SingleExpectDefault.ShouldBe(TimeSpan.FromSeconds(3));
+            TestKitSettings.ExpectNoMessageDefault.ShouldBe(TimeSpan.FromSeconds(3));
             TestKitSettings.TestEventFilterLeeway.ShouldBe(TimeSpan.FromSeconds(3));
             TestKitSettings.TestTimeFactor.ShouldBe(1);
             var callingThreadDispatcherTypeName = typeof(CallingThreadDispatcherConfigurator).FullName + ", " + typeof(CallingThreadDispatcher).Assembly.GetName().Name;

src/core/Akka.TestKit/Internal/Reference.conf

@@ -23,6 +23,10 @@ akka {
     # by default
     single-expect-default = 3s
 
+    # duration to wait in expectNoMsg
+    # by default
+    expect-no-message-default = 3s
+
     # The timeout that is added as an implicit by DefaultTimeout trait 
     # This is used for Ask-pattern
     default-timeout = 5s

src/core/Akka.TestKit/TestKitBase.cs

@@ -230,6 +230,7 @@ protected void InitializeTest(ActorSystem system, Config config, string actorSys
         }
 
         private TimeSpan SingleExpectDefaultTimeout { get { return _testState.TestKitSettings.SingleExpectDefault; } }
+        private TimeSpan ExpectNoMessageDefaultTimeout { get { return _testState.TestKitSettings.ExpectNoMessageDefault; } }
 
         /// <summary>
         /// The <see cref="ActorSystem"/> that is recreated and used for each test.
@@ -403,6 +404,20 @@ public TimeSpan RemainingOrDefault
             get { return RemainingOr(Dilated(SingleExpectDefaultTimeout)); }
         }
 
+        /// <summary>
+        /// <para>
+        /// Retrieves the time remaining for execution of the innermost enclosing
+        /// <see cref="Within(TimeSpan, Action, TimeSpan?, CancellationToken)">Within</see> block.
+        /// If missing that, then it returns the properly dilated default for this
+        /// case from settings (key: "akka.test.expect-no-message-default").
+        /// </para>
+        /// <remarks>The returned value is always finite.</remarks>
+        /// </summary>
+        public TimeSpan NoMessageRemainingOrDefault
+        {
+            get { return RemainingOr(Dilated(ExpectNoMessageDefaultTimeout)); }
+        }
+
         /// <summary>
         /// <para>
         /// Retrieves the time remaining for execution of the innermost enclosing

src/core/Akka.TestKit/TestKitBase_Expect.cs

@@ -458,7 +458,7 @@ private async ValueTask<MessageEnvelope> InternalExpectMsgEnvelopeAsync<T>(
         /// 
         /// Wait time is bounded by remaining time for execution of the innermost enclosing 'within'
         /// block, if inside a 'within' block; otherwise by the config value 
-        /// "akka.test.single-expect-default".
+        /// "akka.test.expect-no-message-default".
         /// </summary>
         public void ExpectNoMsg(CancellationToken cancellationToken = default)
         {
@@ -469,7 +469,7 @@ public void ExpectNoMsg(CancellationToken cancellationToken = default)
         /// <inheritdoc cref="ExpectNoMsg(CancellationToken)"/>
         public async ValueTask ExpectNoMsgAsync(CancellationToken cancellationToken = default)
         {
-            await InternalExpectNoMsgAsync(RemainingOrDefault, cancellationToken)
+            await InternalExpectNoMsgAsync(NoMessageRemainingOrDefault, cancellationToken)
                 .ConfigureAwait(false);
         }
 

src/core/Akka.TestKit/TestKitSettings.cs

@@ -18,6 +18,7 @@ public class TestKitSettings : IExtension
     {
         private readonly TimeSpan _defaultTimeout;
         private readonly TimeSpan _singleExpectDefault;
+        private readonly TimeSpan _expectNoMessageDefault;
         private readonly TimeSpan _testEventFilterLeeway;
         private readonly double _timefactor;
         private readonly bool _logTestKitCalls;
@@ -36,6 +37,7 @@ public TestKitSettings(Config config)
 
             _defaultTimeout = config.GetTimeSpan("akka.test.default-timeout", null, allowInfinite:false);
             _singleExpectDefault = config.GetTimeSpan("akka.test.single-expect-default", null, allowInfinite: false);
+            _expectNoMessageDefault = config.GetTimeSpan("akka.test.expect-no-message-default", null, allowInfinite: false);
             _testEventFilterLeeway = config.GetTimeSpan("akka.test.filter-leeway", null, allowInfinite: false);
             _timefactor = config.GetDouble("akka.test.timefactor", 0);
             _logTestKitCalls = config.GetBoolean("akka.test.testkit.debug", false);
@@ -54,6 +56,9 @@ public TestKitSettings(Config config)
         /// <summary>Gets the config value "akka.test.single-expect-default". It is always finite.</summary>
         public TimeSpan SingleExpectDefault { get { return _singleExpectDefault; } }
 
+        /// <summary>Gets the config value "akka.test.expect-no-message-default". It is always finite.</summary>
+        public TimeSpan ExpectNoMessageDefault { get { return _expectNoMessageDefault; } }
+
         /// <summary>Gets the config value "akka.test.filter-leeway".  It is always finite.</summary>
         public TimeSpan TestEventFilterLeeway { get { return _testEventFilterLeeway; } }