diff --git a/test/unit/Elsa.Activities.UnitTests/Http/WriteHttpResponseTests.cs b/test/unit/Elsa.Activities.UnitTests/Http/WriteHttpResponseTests.cs
new file mode 100644
index 000000000..912094126
--- /dev/null
+++ b/test/unit/Elsa.Activities.UnitTests/Http/WriteHttpResponseTests.cs
@@ -0,0 +1,300 @@
+using System.Net;
+using System.Text;
+using Elsa.Http;
+using Elsa.Http.ContentWriters;
+using Elsa.Http.Options;
+using Elsa.Http.Parsers;
+using Elsa.Testing.Shared;
+using Elsa.Workflows;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using NSubstitute;
+
+namespace Elsa.Activities.UnitTests.Http;
+
+public class WriteHttpResponseTests
+{
+    [Theory]
+    [InlineData(HttpStatusCode.OK, 200)]
+    [InlineData(HttpStatusCode.Created, 201)]
+    [InlineData(HttpStatusCode.NotFound, 404)]
+    [InlineData(HttpStatusCode.InternalServerError, 500)]
+    public async Task Should_Set_Correct_Status_Code(HttpStatusCode statusCode, int expectedStatusCode)
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        activity.StatusCode = new Input<HttpStatusCode>(statusCode);
+
+        // Act
+        var context = await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.Equal(expectedStatusCode, httpContext.Response.StatusCode);
+        Assert.True(context.IsCompleted);
+    }
+
+    [Theory]
+    [InlineData("Hello World", "text/plain", "Hello World")]
+    [InlineData("{\"name\": \"John\"}", "application/json", "{\"name\": \"John\"}")]
+    [InlineData("<root><name>John</name></root>", "application/xml", "<root><name>John</name></root>")]
+    public async Task Should_Write_String_Content_With_Correct_Content_Type(string content, string contentType, string expectedContent)
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        activity.Content = new Input<object?>(content);
+        activity.ContentType = new Input<string?>(contentType);
+
+        // Act
+        await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.Equal(contentType, httpContext.Response.ContentType);
+        var responseContent = GetResponseContent(httpContext);
+        Assert.Equal(expectedContent, responseContent);
+    }
+
+    [Fact]
+    public async Task Should_Serialize_Object_To_Json_When_No_Content_Type_Specified()
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        var testObject = new { Name = "John", Age = 30 };
+        activity.Content = new Input<object?>(testObject);
+
+        // Act
+        await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.Equal("application/json", httpContext.Response.ContentType);
+        var responseContent = GetResponseContent(httpContext);
+        Assert.Contains("John", responseContent);
+        Assert.Contains("30", responseContent);
+    }
+
+    [Theory]
+    [InlineData("Custom-Header", "CustomValue")]
+    [InlineData("X-Rate-Limit", "100")]
+    [InlineData("Cache-Control", "no-cache")]
+    public async Task Should_Add_Response_Headers(string headerName, string headerValue)
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        var headers = new HttpHeaders { { headerName, new[] { headerValue } } };
+        activity.ResponseHeaders = new Input<HttpHeaders?>(headers);
+
+        // Act
+        await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.True(httpContext.Response.Headers.ContainsKey(headerName));
+        Assert.Equal(headerValue, httpContext.Response.Headers[headerName]);
+    }
+
+    [Fact]
+    public async Task Should_Add_Multiple_Response_Headers()
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        var headers = new HttpHeaders
+        {
+            { "Custom-Header-1", new[] { "Value1" } },
+            { "Custom-Header-2", new[] { "Value2" } },
+            { "X-Rate-Limit", new[] { "100" } }
+        };
+        activity.ResponseHeaders = new Input<HttpHeaders?>(headers);
+
+        // Act
+        await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.True(httpContext.Response.Headers.ContainsKey("Custom-Header-1"));
+        Assert.True(httpContext.Response.Headers.ContainsKey("Custom-Header-2"));
+        Assert.True(httpContext.Response.Headers.ContainsKey("X-Rate-Limit"));
+        Assert.Equal("Value1", httpContext.Response.Headers["Custom-Header-1"]);
+        Assert.Equal("Value2", httpContext.Response.Headers["Custom-Header-2"]);
+        Assert.Equal("100", httpContext.Response.Headers["X-Rate-Limit"]);
+    }
+
+    [Fact]
+    public async Task Should_Not_Write_Content_When_Status_Code_Is_NoContent()
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        activity.StatusCode = new Input<HttpStatusCode>(HttpStatusCode.NoContent);
+        activity.Content = new Input<object?>("This should not be written");
+
+        // Act
+        await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.Equal(204, httpContext.Response.StatusCode);
+        var responseContent = GetResponseContent(httpContext);
+        Assert.Empty(responseContent);
+    }
+
+    [Fact]
+    public async Task Should_Handle_Null_Content()
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        activity.Content = new Input<object?>((object?)null);
+
+        // Act
+        await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.Equal(200, httpContext.Response.StatusCode);
+        var responseContent = GetResponseContent(httpContext);
+        Assert.Empty(responseContent);
+    }
+
+    [Fact]
+    public async Task Should_Call_CompleteAsync_When_WriteHttpResponseSynchronously_Is_True()
+    {
+        // Arrange
+        var activity = new WriteHttpResponse();
+        var mockHttpContext = Substitute.For<HttpContext>();
+        var mockResponse = Substitute.For<HttpResponse>();
+        var mockHeaders = new HeaderDictionary();
+        var responseBody = new MemoryStream();
+        
+        mockResponse.StatusCode.Returns(200);
+        mockResponse.Headers.Returns(mockHeaders);
+        mockResponse.Body.Returns(responseBody);
+        mockHttpContext.Response.Returns(mockResponse);
+
+        // Act
+        await ExecuteActivityAsync(activity, mockHttpContext, writeResponseSynchronously: true);
+
+        // Assert
+        await mockResponse.Received(1).CompleteAsync();
+    }
+
+    [Fact]
+    public async Task Should_Not_Call_CompleteAsync_When_WriteHttpResponseSynchronously_Is_False()
+    {
+        // Arrange
+        var activity = new WriteHttpResponse();
+        var mockHttpContext = Substitute.For<HttpContext>();
+        var mockResponse = Substitute.For<HttpResponse>();
+        var mockHeaders = new HeaderDictionary();
+        var responseBody = new MemoryStream();
+        
+        mockResponse.StatusCode.Returns(200);
+        mockResponse.Headers.Returns(mockHeaders);
+        mockResponse.Body.Returns(responseBody);
+        mockHttpContext.Response.Returns(mockResponse);
+
+        // Act
+        await ExecuteActivityAsync(activity, mockHttpContext, writeResponseSynchronously: false);
+
+        // Assert
+        await mockResponse.DidNotReceive().CompleteAsync();
+    }
+
+    [Fact]
+    public async Task Should_Create_Bookmark_When_No_HttpContext_Available()
+    {
+        // Arrange
+        var activity = new WriteHttpResponse();
+        var fixture = new ActivityTestFixture(activity);
+        fixture.ConfigureServices(services =>
+        {
+            var mockHttpContextAccessor = Substitute.For<IHttpContextAccessor>();
+            mockHttpContextAccessor.HttpContext.Returns((HttpContext?)null);
+            services.AddSingleton(mockHttpContextAccessor);
+            services.AddSingleton(CreateMockHttpActivityOptions());
+            AddHttpContentFactories(services);
+            services.AddSingleton(Substitute.For<IStimulusHasher>());
+        });
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.False(context.IsCompleted);
+        var bookmarks = context.WorkflowExecutionContext.Bookmarks.ToList();
+        Assert.Single(bookmarks);
+    }
+
+    [Fact]
+    public async Task Should_Use_Default_Status_Code_When_Not_Specified()
+    {
+        // Arrange
+        var (activity, httpContext) = CreateWriteHttpResponseActivity();
+        // StatusCode is not set, should default to OK (200)
+
+        // Act
+        await ExecuteActivityAsync(activity, httpContext);
+
+        // Assert
+        Assert.Equal(200, httpContext.Response.StatusCode);
+    }
+    
+    private static (WriteHttpResponse activity, HttpContext httpContext) CreateWriteHttpResponseActivity()
+    {
+        var activity = new WriteHttpResponse();
+        var httpContext = new DefaultHttpContext
+        {
+            Response =
+            {
+                Body = new MemoryStream()
+            }
+        };
+
+        return (activity, httpContext);
+    }
+
+    private static async Task<ActivityExecutionContext> ExecuteActivityAsync(WriteHttpResponse activity, HttpContext httpContext, bool writeResponseSynchronously = false)
+    {
+        var fixture = new ActivityTestFixture(activity);
+        fixture.ConfigureServices(services =>
+        {
+            var mockHttpContextAccessor = Substitute.For<IHttpContextAccessor>();
+            mockHttpContextAccessor.HttpContext.Returns(httpContext);
+            services.AddSingleton(mockHttpContextAccessor);
+            services.AddSingleton(CreateMockHttpActivityOptions(writeResponseSynchronously));
+            AddHttpContentFactories(services);
+            AddHttpContentParsers(services);
+            services.AddLogging();
+        });
+
+        return await fixture.ExecuteAsync();
+    }
+
+    private static IOptions<HttpActivityOptions> CreateMockHttpActivityOptions(bool writeResponseSynchronously = false)
+    {
+        var options = new HttpActivityOptions
+        {
+            WriteHttpResponseSynchronously = writeResponseSynchronously
+        };
+        var mockOptions = Substitute.For<IOptions<HttpActivityOptions>>();
+        mockOptions.Value.Returns(options);
+        return mockOptions;
+    }
+
+    private static void AddHttpContentFactories(IServiceCollection services)
+    {
+        services.AddSingleton<IHttpContentFactory, JsonContentFactory>();
+        services.AddSingleton<IHttpContentFactory, TextContentFactory>();
+        services.AddSingleton<IHttpContentFactory, XmlContentFactory>();
+        services.AddSingleton<IHttpContentFactory, FormUrlEncodedHttpContentFactory>();
+    }
+
+    private static void AddHttpContentParsers(IServiceCollection services)
+    {
+        services.AddSingleton<IHttpContentParser, JsonHttpContentParser>();
+        services.AddSingleton<IHttpContentParser, PlainTextHttpContentParser>();
+        services.AddSingleton<IHttpContentParser, XmlHttpContentParser>();
+        services.AddSingleton<IHttpContentParser, TextHtmlHttpContentParser>();
+        services.AddSingleton<IHttpContentParser, FileHttpContentParser>();
+    }
+
+    private static string GetResponseContent(HttpContext httpContext)
+    {
+        httpContext.Response.Body.Seek(0, SeekOrigin.Begin);
+        using var reader = new StreamReader(httpContext.Response.Body);
+        return reader.ReadToEnd();
+    }
+}
diff --git a/test/unit/Elsa.Activities.UnitTests/Looping/ForTests.cs b/test/unit/Elsa.Activities.UnitTests/Looping/ForTests.cs
new file mode 100644
index 000000000..4428660ec
--- /dev/null
+++ b/test/unit/Elsa.Activities.UnitTests/Looping/ForTests.cs
@@ -0,0 +1,475 @@
+using Elsa.Testing.Shared;
+using Elsa.Extensions;
+using Elsa.Workflows;
+using Elsa.Workflows.Behaviors;
+using Elsa.Workflows.Exceptions;
+
+namespace Elsa.Activities.UnitTests.Looping;
+
+public class ForTests
+{
+    [Theory]
+    [InlineData(1, 3, 1)] // Ascending loop
+    [InlineData(5, 1, -1)] // Descending loop  
+    [InlineData(-1, -5, -1)] // Descending negative loop
+    public async Task ExecutesValidLoopConfigurations_SchedulesChildActivity(int start, int end, int step)
+    {
+        // Arrange
+        var mockBody = new MockBodyActivity();
+        var forActivity = new For(start, end, step) { Body = mockBody };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+        Assert.Equal(start, currentValue);
+        
+        // Verify that child activity is scheduled for valid configurations
+        Assert.True(context.HasScheduledActivity(mockBody), "Expected child activity to be scheduled");
+    }
+
+    [Theory]
+    [InlineData(1, 3, true)] // Inclusive bounds
+    [InlineData(1, 3, false)] // Exclusive bounds
+    [InlineData(5, 5, true)] // Empty range inclusive
+    [InlineData(5, 5, false)] // Empty range exclusive
+    public async Task ExecutesBoundaryConditions(int start, int end, bool inclusive)
+    {
+        // Arrange
+        var mockBody = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End = new Input<int>(end),
+            Step = new Input<int>(1),
+            OuterBoundInclusive = new Input<bool>(inclusive),
+            Body = mockBody
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        bool shouldSchedule = ShouldExecuteLoopWithBounds(start, end, 1, inclusive);
+        Assert.Equal(shouldSchedule, context.HasScheduledActivity(mockBody));
+        
+        if (shouldSchedule)
+        {
+            var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+            Assert.Equal(start, currentValue);
+        }
+    }
+
+    [Theory]
+    [InlineData(5, 1, 1)] // Positive step with descending range - won't execute
+    [InlineData(1, 5, -1)] // Negative step with ascending range - won't execute  
+    public async Task SkipsLoopWhenInvalidConfiguration(int start, int end, int step)
+    {
+        // Arrange
+        var mockBody = new MockBodyActivity();
+        var forActivity = new For(start, end, step) { Body = mockBody };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.False(context.HasScheduledActivity(mockBody));
+    }
+
+    [Fact]
+    public async Task BodyIsNull_DoesNotScheduleActivity()
+    {
+        // Arrange
+        var forActivity = new For(1, 5, 1) { Body = null };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        var allScheduledActivities = context.WorkflowExecutionContext.Scheduler.List().ToList();
+        Assert.Empty(allScheduledActivities);
+    }
+
+    [Fact]
+    public async Task CurrentValueOutputTypeCheck_PreservesIntegerType()
+    {
+        // Arrange
+        var mockBody = new MockBodyActivity(); 
+        var forActivity = new For(1, 3, 1) { Body = mockBody };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+        Assert.IsType<int>(currentValue);
+        Assert.Equal(1, currentValue);
+    }
+
+    [Theory]
+    [InlineData(0, 5, true)]  // Start with default value (0), should execute
+    [InlineData(1, 0, false)] // End with explicit zero value, should not execute (wrong direction)
+    public async Task HandlesDefaultValues(int start, int end, bool shouldExecute)
+    {
+        // Arrange
+        var mockBody = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End = new Input<int>(end),
+            Step = new Input<int>(1),
+            Body = mockBody
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.Equal(shouldExecute, context.HasScheduledActivity(mockBody));
+        
+        if (shouldExecute)
+        {
+            var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+            Assert.Equal(start, currentValue);
+        }
+    }
+
+    [Fact]
+    public void VerifyActivityAttributes()
+    {
+        // Arrange
+        var forActivity = new For();
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act & Assert
+        fixture.AssertActivityAttributes(
+            expectedNamespace: "Elsa",
+            expectedKind: ActivityKind.Action,
+            expectedCategory: "Looping", 
+            expectedDisplayName: null,
+            expectedDescription: "Iterate over a sequence of steps between a start and an end number."
+        );
+    }
+
+    [Fact]
+    public void VerifyBreakBehaviorIsRegistered()
+    {
+        // Arrange
+        var forActivity = new For();
+
+        // Act & Assert
+        var breakBehavior = forActivity.Behaviors.OfType<BreakBehavior>().FirstOrDefault();
+        Assert.NotNull(breakBehavior);
+    }
+
+    [Fact]
+    public void DefaultPropertyValues()
+    {
+        // Arrange
+        var forActivity = new For();
+
+        // Act & Assert
+        Assert.NotNull(forActivity.Start);
+        Assert.NotNull(forActivity.End);
+        Assert.NotNull(forActivity.Step);
+        Assert.NotNull(forActivity.OuterBoundInclusive);
+    }
+
+    [Theory]
+    [InlineData(1, 3, 1, true)]
+    [InlineData(3, 1, -1, true)]
+    [InlineData(5, 5, 1, true)]
+    [InlineData(1, 5, 0, true)] // Zero step - actually schedules activity (infinite loop potential)
+    [InlineData(5, 1, 1, false)] // Wrong direction
+    [InlineData(1, 5, -1, false)] // Wrong direction
+    public async Task LoopDecisionLogic_ValidatesCorrectly(int start, int end, int step, bool shouldExecute)
+    {
+        // Arrange
+        var mockBody = new MockBodyActivity();
+        var forActivity = new For(start, end, step) { Body = mockBody };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.Equal(shouldExecute, context.HasScheduledActivity(mockBody));
+    }
+    
+    // Zero step with different bounds & inclusivity (current contract: schedules at least first body)
+    [Theory]
+    [InlineData(1, 5, true,  true)]  // within ascending range, inclusive -> schedules
+    [InlineData(1, 5, false, true)]  // within ascending range, exclusive -> schedules (start < end)
+    [InlineData(5, 1, true,  false)] // start > end with ascending step (step=0 treated as positive) -> no schedule
+    [InlineData(5, 1, false, false)] // start > end with ascending step (step=0 treated as positive) -> no schedule
+    [InlineData(6, 5, true,  false)] // start already outside ascending range -> no schedule
+    [InlineData(0, -1, false, false)]// start already outside descending (exclusive) -> no schedule
+    public async Task ZeroStep_RespectsInitialBoundCheck(int start, int end, bool inclusive, bool shouldSchedule)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End = new Input<int>(end),
+            Step = new Input<int>(0), // zero step: current contract allows first schedule
+            OuterBoundInclusive = new Input<bool>(inclusive),
+            Body = body
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.Equal(shouldSchedule, context.HasScheduledActivity(body));
+        if (shouldSchedule)
+        {
+            var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+            Assert.IsType<int>(currentValue);
+            Assert.Equal(start, currentValue);
+        }
+    }
+    
+    [Theory]
+    [InlineData(1, 5, 10)]   // ascending, step too large
+    [InlineData(5, 1, -10)]  // descending, step too large
+    public async Task StepLargerThanRange_StillSchedulesOnce(int start, int end, int step)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For(start, end, step) { Body = body };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.True(context.HasScheduledActivity(body));
+        var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+        Assert.Equal(start, currentValue);
+    }
+    
+    [Theory]
+    [InlineData(5, 5,  1)]
+    [InlineData(5, 5, -1)]
+    public async Task EqualBounds_Exclusive_DoesNotExecute(int start, int end, int step)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End = new Input<int>(end),
+            Step = new Input<int>(step),
+            OuterBoundInclusive = new Input<bool>(false),
+            Body = body
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.False(context.HasScheduledActivity(body));
+    }
+    
+    [Theory]
+    [InlineData(3, 1, -1, true,  true)]  // inclusive: start (3) >= end (1) -> schedules
+    [InlineData(3, 3, -1, false, false)] // exclusive: start == end -> no schedule
+    [InlineData(2, 3, -1, true,  false)] // start already below end for descending -> no schedule
+    public async Task Descending_InclusiveExclusive_OffByOne(int start, int end, int step, bool inclusive, bool shouldSchedule)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End = new Input<int>(end),
+            Step = new Input<int>(step),
+            OuterBoundInclusive = new Input<bool>(inclusive),
+            Body = body
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.Equal(shouldSchedule, context.HasScheduledActivity(body));
+    }
+    
+    [Theory]
+    [InlineData(int.MaxValue, int.MaxValue,  1, true,  true)]  // inclusive equal -> schedules
+    [InlineData(int.MaxValue, int.MaxValue,  1, false, false)] // exclusive equal -> no schedule
+    [InlineData(int.MinValue, int.MinValue, -1, true,  true)]
+    [InlineData(int.MinValue, int.MinValue, -1, false, false)]
+    public async Task ExtremeBounds_NoOverflow_OnInitialDecision(int start, int end, int step, bool inclusive, bool shouldSchedule)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End = new Input<int>(end),
+            Step = new Input<int>(step),
+            OuterBoundInclusive = new Input<bool>(inclusive),
+            Body = body
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.Equal(shouldSchedule, context.HasScheduledActivity(body));
+        if (shouldSchedule)
+        {
+            var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+            Assert.Equal(start, currentValue);
+        }
+    }
+    
+    [Theory]
+    [InlineData("start")]
+    [InlineData("end")]
+    [InlineData("step")]
+    public async Task InputExpressions_Throw_DoNotSchedule(string which)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = which == "start" ? new Input<int>((Func<int>)(() => throw new ApplicationException("start!"))) : new Input<int>(1),
+            End   = which == "end"   ? new Input<int>((Func<int>)(() => throw new ApplicationException("end!")))   : new Input<int>(3),
+            Step  = which == "step"  ? new Input<int>((Func<int>)(() => throw new ApplicationException("step!")))  : new Input<int>(1),
+            Body = body
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act + Assert
+        var ex = await Assert.ThrowsAsync<InputEvaluationException>(() => fixture.ExecuteAsync());
+        Assert.Contains(which, ex.Message, StringComparison.InvariantCultureIgnoreCase);
+    }
+    
+    [Fact]
+    public async Task BodyThrows_ActivitySchedules_WithoutBreaking()
+    {
+        // Arrange
+        var body = new ThrowingBody(new InvalidOperationException("boom"));
+        var forActivity = new For(1, 3, 1) { Body = body };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+        
+        // Assert
+        Assert.NotNull(context);
+        Assert.True(context.HasScheduledActivity(body));
+    }
+    
+    [Theory]
+    [InlineData(true,  1, 5)]  // positive step computed -> ascending executes
+    [InlineData(false, 5, 1)]  // negative step computed -> descending executes
+    public async Task DynamicStep_EvaluatedAtExecutionTime(bool usePositive, int start, int end)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var stepValue = usePositive ? 1 : -1; // Compute step value directly from parameter
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End   = new Input<int>(end),
+            Step  = new Input<int>((Func<int>)(() => stepValue)),
+            Body  = body
+        };
+
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.True(context.HasScheduledActivity(body));
+        var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+        Assert.Equal(start, currentValue);
+    }
+    
+    [Fact]
+    public async Task NegativeStart_NegativeStep_CurrentValueIsIntAndMatchesStart()
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For(-2, -10, -2) { Body = body };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.True(context.HasScheduledActivity(body));
+        var currentValue = context.GetActivityOutput(() => forActivity.CurrentValue);
+        Assert.IsType<int>(currentValue);
+        Assert.Equal(-2, currentValue);
+    }
+    
+    [Theory]
+    [InlineData(10, 5,  1, true)]  // ascending + inclusive, start > end -> no schedule
+    [InlineData(10, 5,  1, false)] // ascending + exclusive, start > end -> no schedule
+    [InlineData(0,  5, -1, true)]  // descending + inclusive, start < end -> no schedule
+    [InlineData(0,  5, -1, false)] // descending + exclusive, start < end -> no schedule
+    public async Task StartOutsideRange_DoesNotSchedule(int start, int end, int step, bool inclusive)
+    {
+        // Arrange
+        var body = new MockBodyActivity();
+        var forActivity = new For
+        {
+            Start = new Input<int>(start),
+            End   = new Input<int>(end),
+            Step  = new Input<int>(step),
+            OuterBoundInclusive = new Input<bool>(inclusive),
+            Body = body
+        };
+        var fixture = new ActivityTestFixture(forActivity);
+
+        // Act
+        var context = await fixture.ExecuteAsync();
+
+        // Assert
+        Assert.False(context.HasScheduledActivity(body));
+    }
+    
+    private static bool ShouldExecuteLoopWithBounds(int start, int end, int step, bool inclusive)
+    {
+        // Match the actual For activity logic exactly
+        var increment = step >= 0;
+
+        return increment && inclusive ? start <= end
+            : increment && !inclusive ? start < end
+            : !increment && inclusive ? start >= end
+            : !increment && !inclusive && start > end;
+    }
+
+    /// <summary>
+    /// Mock activity to represent the body of the For loop
+    /// </summary>
+    private class MockBodyActivity : Activity
+    {
+        protected override ValueTask ExecuteAsync(ActivityExecutionContext context) => ValueTask.CompletedTask;
+    }
+    
+    /// <summary>
+    /// A body that throws a provided exception when executed
+    /// </summary>
+    private class ThrowingBody(Exception exception) : Activity
+    {
+        protected override ValueTask ExecuteAsync(ActivityExecutionContext context) => throw exception;
+    }
+}