diff --git a/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs b/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
index 7347d61f..a9386a73 100644
--- a/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
+++ b/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
@@ -8,8 +8,22 @@ namespace Microsoft.DurableTask.Client.Tests;
 
 public class ServiceCollectionExtensionsTests
 {
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("MyBuilder")]
+    public void AddDurableTaskClient_SameInstance(string? name)
+    {
+        ServiceCollection services = new();
+        IDurableTaskClientBuilder actual1 = services.AddDurableTaskClient(name);
+        IDurableTaskClientBuilder actual2 = services.AddDurableTaskClient(name);
+
+        actual1.Should().NotBeNull();
+        actual1.Should().BeSameAs(actual2);
+    }
+
     [Fact]
-    public void AddDurableTaskClient_SameInstance()
+    public void AddDurableTaskClient_SameInstance2()
     {
         ServiceCollection services = new();
         IDurableTaskClientBuilder? actual1 = null;
@@ -21,6 +35,73 @@ public void AddDurableTaskClient_SameInstance()
         actual1.Should().BeSameAs(actual2);
     }
 
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("MyBuilder")]
+    public void AddDurableTaskClient_SameInstance3(string name)
+    {
+        ServiceCollection services = new();
+        IDurableTaskClientBuilder? actual1 = null;
+        IDurableTaskClientBuilder? actual2 = null;
+        services.AddDurableTaskClient(name, builder => actual1 = builder);
+        services.AddDurableTaskClient(name, builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual1.Should().BeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskClient_SameInstance4()
+    {
+        ServiceCollection services = new();
+        IDurableTaskClientBuilder actual1 = services.AddDurableTaskClient();
+        IDurableTaskClientBuilder? actual2 = null;
+        services.AddDurableTaskClient(builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual1.Should().BeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskClient_DifferentNames_NotSame()
+    {
+        ServiceCollection services = new();
+        IDurableTaskClientBuilder actual1 = services.AddDurableTaskClient();
+        IDurableTaskClientBuilder actual2 = services.AddDurableTaskClient("MyBuilder");
+
+        actual1.Should().NotBeNull();
+        actual2.Should().NotBeNull();
+        actual1.Should().NotBeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskClient_DifferentNames_NotSame2()
+    {
+        ServiceCollection services = new();
+        IDurableTaskClientBuilder? actual1 = null;
+        IDurableTaskClientBuilder? actual2 = null;
+        services.AddDurableTaskClient(builder => actual1 = builder);
+        services.AddDurableTaskClient("MyBuilder", builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual2.Should().NotBeNull();
+        actual1.Should().NotBeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskClient_DifferentNames_NotSame3()
+    {
+        ServiceCollection services = new();
+        IDurableTaskClientBuilder actual1 = services.AddDurableTaskClient();
+        IDurableTaskClientBuilder? actual2 = null;
+        services.AddDurableTaskClient("MyBuilder", builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual2.Should().NotBeNull();
+        actual1.Should().NotBeSameAs(actual2);
+    }
+
     [Fact]
     public void AddDurableTaskClient_HostedServiceAdded()
     {
diff --git a/test/Worker/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs b/test/Worker/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
index 672d6eee..e584da9c 100644
--- a/test/Worker/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
+++ b/test/Worker/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
@@ -9,8 +9,22 @@ namespace Microsoft.DurableTask.Worker.Tests;
 
 public class ServiceCollectionExtensionsTests
 {
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("MyBuilder")]
+    public void AddDurableTaskWorker_SameInstance(string? name)
+    {
+        ServiceCollection services = new();
+        IDurableTaskWorkerBuilder actual1 = services.AddDurableTaskWorker(name);
+        IDurableTaskWorkerBuilder actual2 = services.AddDurableTaskWorker(name);
+
+        actual1.Should().NotBeNull();
+        actual1.Should().BeSameAs(actual2);
+    }
+
     [Fact]
-    public void AddDurableTaskWorker_SameInstance()
+    public void AddDurableTaskWorker_SameInstance2()
     {
         ServiceCollection services = new();
         IDurableTaskWorkerBuilder? actual1 = null;
@@ -22,6 +36,73 @@ public void AddDurableTaskWorker_SameInstance()
         actual1.Should().BeSameAs(actual2);
     }
 
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("MyBuilder")]
+    public void AddDurableTaskWorker_SameInstance3(string name)
+    {
+        ServiceCollection services = new();
+        IDurableTaskWorkerBuilder? actual1 = null;
+        IDurableTaskWorkerBuilder? actual2 = null;
+        services.AddDurableTaskWorker(name, builder => actual1 = builder);
+        services.AddDurableTaskWorker(name, builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual1.Should().BeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskWorker_SameInstance4()
+    {
+        ServiceCollection services = new();
+        IDurableTaskWorkerBuilder actual1 = services.AddDurableTaskWorker();
+        IDurableTaskWorkerBuilder? actual2 = null;
+        services.AddDurableTaskWorker(builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual1.Should().BeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskWorker_DifferentNames_NotSame()
+    {
+        ServiceCollection services = new();
+        IDurableTaskWorkerBuilder actual1 = services.AddDurableTaskWorker();
+        IDurableTaskWorkerBuilder actual2 = services.AddDurableTaskWorker("MyBuilder");
+
+        actual1.Should().NotBeNull();
+        actual2.Should().NotBeNull();
+        actual1.Should().NotBeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskWorker_DifferentNames_NotSame2()
+    {
+        ServiceCollection services = new();
+        IDurableTaskWorkerBuilder? actual1 = null;
+        IDurableTaskWorkerBuilder? actual2 = null;
+        services.AddDurableTaskWorker(builder => actual1 = builder);
+        services.AddDurableTaskWorker("MyBuilder", builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual2.Should().NotBeNull();
+        actual1.Should().NotBeSameAs(actual2);
+    }
+
+    [Fact]
+    public void AddDurableTaskWorker_DifferentNames_NotSame3()
+    {
+        ServiceCollection services = new();
+        IDurableTaskWorkerBuilder actual1 = services.AddDurableTaskWorker();
+        IDurableTaskWorkerBuilder? actual2 = null;
+        services.AddDurableTaskWorker("MyBuilder", builder => actual2 = builder);
+
+        actual1.Should().NotBeNull();
+        actual2.Should().NotBeNull();
+        actual1.Should().NotBeSameAs(actual2);
+    }
+
     [Fact]
     public void AddDurableTaskWorker_HostedServiceAdded()
     {