diff --git a/test/Savvyio.Extensions.NATS.Tests/Commands/NatsCommandQueueOptionsTest.cs b/test/Savvyio.Extensions.NATS.Tests/Commands/NatsCommandQueueOptionsTest.cs
index 2d864fc..ad8c746 100644
--- a/test/Savvyio.Extensions.NATS.Tests/Commands/NatsCommandQueueOptionsTest.cs
+++ b/test/Savvyio.Extensions.NATS.Tests/Commands/NatsCommandQueueOptionsTest.cs
@@ -69,6 +69,18 @@ public void Heartbeat_Can_Be_Set_Manually()
             Assert.Equal(TimeSpan.FromSeconds(10), options.Heartbeat);
         }
 
+        [Fact]
+        public void Heartbeat_Can_Be_Overridden_After_Expires()
+        {
+            var options = new NatsCommandQueueOptions();
+
+            options.Expires = TimeSpan.FromSeconds(60);
+            Assert.Equal(TimeSpan.FromSeconds(5), options.Heartbeat);
+
+            options.Heartbeat = TimeSpan.FromSeconds(15);
+            Assert.Equal(TimeSpan.FromSeconds(15), options.Heartbeat);
+        }
+
         [Fact]
         public void StreamName_And_ConsumerName_Can_Be_Set_And_Gotten()
         {
diff --git a/test/Savvyio.Extensions.RabbitMQ.Tests/RabbitMqMessageTest.cs b/test/Savvyio.Extensions.RabbitMQ.Tests/RabbitMqMessageTest.cs
index f002e13..fada94c 100644
--- a/test/Savvyio.Extensions.RabbitMQ.Tests/RabbitMqMessageTest.cs
+++ b/test/Savvyio.Extensions.RabbitMQ.Tests/RabbitMqMessageTest.cs
@@ -101,6 +101,33 @@ public async Task EnsureConnectivityAsync_InitializesConnectionAndChannel_Once()
             factoryMock.Verify(f => f.CreateConnectionAsync(It.IsAny<CancellationToken>()), Times.Once);
         }
 
+        [Fact]
+        public async Task EnsureConnectivityAsync_IsThreadSafe_WhenCalledConcurrently()
+        {
+            var marshaller = new Mock<IMarshaller>().Object;
+            var options = new RabbitMqMessageOptions { AmqpUrl = new Uri("amqp://localhost:5672") };
+
+            var connectionMock = new Mock<IConnection>();
+            var channelMock = new Mock<IChannel>();
+            connectionMock.Setup(c => c.CreateChannelAsync(It.IsAny<CreateChannelOptions?>(), It.IsAny<CancellationToken>()))
+                .ReturnsAsync(channelMock.Object);
+
+            var factoryMock = new Mock<IConnectionFactory>();
+            factoryMock.Setup(f => f.CreateConnectionAsync(It.IsAny<CancellationToken>()))
+                .ReturnsAsync(connectionMock.Object);
+
+            var sut = new TestRabbitMqMessage(marshaller, options);
+            typeof(RabbitMqMessage)
+                .GetProperty("RabbitMqFactory", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)
+                .SetValue(sut, factoryMock.Object);
+
+            await Task.WhenAll(
+                sut.CallEnsureConnectivityAsync(),
+                sut.CallEnsureConnectivityAsync());
+
+            factoryMock.Verify(f => f.CreateConnectionAsync(It.IsAny<CancellationToken>()), Times.Once);
+        }
+
         [Fact]
         public async Task OnDisposeManagedResourcesAsync_DisposesChannelAndConnection()
         {
diff --git a/test/Savvyio.Extensions.SimpleQueueService.Tests/AmazonMessageReceiveOptionsTest.cs b/test/Savvyio.Extensions.SimpleQueueService.Tests/AmazonMessageReceiveOptionsTest.cs
index a5b140c..1ef3e89 100644
--- a/test/Savvyio.Extensions.SimpleQueueService.Tests/AmazonMessageReceiveOptionsTest.cs
+++ b/test/Savvyio.Extensions.SimpleQueueService.Tests/AmazonMessageReceiveOptionsTest.cs
@@ -45,5 +45,17 @@ public void PollingTimeout_ShouldClampValue_WhenOutsideRangeOfAllowedLimits()
             sut.PollingTimeout = TimeSpan.MaxValue;
             Assert.Equal(TimeSpan.FromSeconds(AmazonMessageOptions.MaxPollingWaitTimeInSeconds), sut.PollingTimeout);
         }
+
+        [Fact]
+        public void VisibilityTimeout_ShouldClampValue_WhenOutsideRangeOfAllowedLimits()
+        {
+            var sut = new AmazonMessageReceiveOptions();
+
+            sut.VisibilityTimeout = TimeSpan.MinValue;
+            Assert.Equal(TimeSpan.Zero, sut.VisibilityTimeout);
+
+            sut.VisibilityTimeout = TimeSpan.FromSeconds(AmazonMessageOptions.MaxVisibilityTimeoutInSeconds + 1);
+            Assert.Equal(TimeSpan.FromSeconds(AmazonMessageOptions.MaxVisibilityTimeoutInSeconds), sut.VisibilityTimeout);
+        }
     }
 }
diff --git a/test/Savvyio.Extensions.SimpleQueueService.Tests/ClientConfigExtensionsTest.cs b/test/Savvyio.Extensions.SimpleQueueService.Tests/ClientConfigExtensionsTest.cs
new file mode 100644
index 0000000..7c56d28
--- /dev/null
+++ b/test/Savvyio.Extensions.SimpleQueueService.Tests/ClientConfigExtensionsTest.cs
@@ -0,0 +1,38 @@
+using Amazon.Runtime;
+using Amazon.SimpleNotificationService;
+using Amazon.SQS;
+using Codebelt.Extensions.Xunit;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Savvyio.Extensions.SimpleQueueService
+{
+    public class ClientConfigExtensionsTest : Test
+    {
+        public ClientConfigExtensionsTest(ITestOutputHelper output) : base(output) { }
+
+        [Fact]
+        public void IsValid_ShouldEvaluateConfigurations()
+        {
+            ClientConfig[] invalid = null;
+            Assert.False(invalid.IsValid());
+
+            var valid = new ClientConfig[] { new AmazonSQSConfig(), new AmazonSimpleNotificationServiceConfig() };
+            Assert.True(valid.IsValid());
+
+            var wrongLength = new ClientConfig[] { new AmazonSQSConfig() };
+            Assert.False(wrongLength.IsValid());
+        }
+
+        [Fact]
+        public void ShouldResolveSpecificConfigurations()
+        {
+            var sqs = new AmazonSQSConfig();
+            var sns = new AmazonSimpleNotificationServiceConfig();
+            ClientConfig[] configs = { sqs, sns };
+
+            Assert.Same(sqs, configs.SimpleQueueService());
+            Assert.Same(sns, configs.SimpleNotificationService());
+        }
+    }
+}
diff --git a/test/Savvyio.Extensions.SimpleQueueService.Tests/EventDriven/StringExtensionsTest.cs b/test/Savvyio.Extensions.SimpleQueueService.Tests/EventDriven/StringExtensionsTest.cs
new file mode 100644
index 0000000..8f7bf59
--- /dev/null
+++ b/test/Savvyio.Extensions.SimpleQueueService.Tests/EventDriven/StringExtensionsTest.cs
@@ -0,0 +1,33 @@
+using System;
+using Codebelt.Extensions.Xunit;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Savvyio.Extensions.SimpleQueueService.EventDriven
+{
+    public class StringExtensionsTest : Test
+    {
+        public StringExtensionsTest(ITestOutputHelper output) : base(output) { }
+
+        [Fact]
+        public void ToSnsUri_ShouldBuildArnWithDefaults()
+        {
+            var uri = "sample-topic".ToSnsUri();
+
+            Assert.Equal(new Uri("arn:aws:sns:eu-west-1:000000000000:sample-topic"), uri);
+        }
+
+        [Fact]
+        public void ToSnsUri_ShouldRespectCustomOptions()
+        {
+            var uri = "topic".ToSnsUri(o =>
+            {
+                o.Partition = "aws";
+                o.Region = "us-east-1";
+                o.AccountId = "123456789012";
+            });
+
+            Assert.Equal(new Uri("arn:aws:sns:us-east-1:123456789012:topic"), uri);
+        }
+    }
+}