Add project files.

test/integration/Elsa.Workflows.IntegrationTests/Scenarios/Composites/Tests.cs

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+using Elsa.Extensions;
+using Elsa.Testing.Shared;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit.Abstractions;
+
+namespace Elsa.Workflows.IntegrationTests.Scenarios.Composites;
+
+public class Tests
+{
+    private readonly IWorkflowRunner _workflowRunner;
+    private readonly CapturingTextWriter _capturingTextWriter = new();
+    private readonly IWorkflowBuilderFactory _workflowBuilderFactory;
+    private readonly IServiceProvider _services;
+
+    public Tests(ITestOutputHelper testOutputHelper)
+    {
+        _services = new TestApplicationBuilder(testOutputHelper)
+            .WithCapturingTextWriter(_capturingTextWriter)
+            .ConfigureElsa(elsa => elsa.UseJavaScript())
+            .Build();
+        _workflowBuilderFactory = _services.GetRequiredService<IWorkflowBuilderFactory>();
+        _workflowRunner = _services.GetRequiredService<IWorkflowRunner>();
+    }
+
+    [Fact(DisplayName = "The main workflow can capture the result of the composite activity")]
+    public async Task Test1()
+    {
+        await _services.PopulateRegistriesAsync();
+        var workflow = await _workflowBuilderFactory.CreateBuilder().BuildWorkflowAsync<SumWorkflow>();
+
+        // Start workflow.
+        await _workflowRunner.RunAsync(workflow);
+
+        // Verify expected output.
+        var lines = _capturingTextWriter.Lines.ToList();
+        Assert.Equal(new[] { "Sum: 3" }, lines);
+    }
+}

test/integration/Elsa.Workflows.IntegrationTests/Scenarios/Composites/Workflows.cs

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+using Elsa.Extensions;
+using Elsa.JavaScript.Activities;
+using Elsa.Workflows.Activities;
+using Elsa.Workflows.Memory;
+using Elsa.Workflows.Models;
+
+namespace Elsa.Workflows.IntegrationTests.Scenarios.Composites;
+
+/// <summary>
+/// A composite activity that sums two inputs and returns the result.
+/// </summary>
+public class Sum : Composite<int>
+{
+    private readonly RunJavaScript _runJavaScript;
+
+    public Input<int> A { get; set; } = null!;
+    public Input<int> B { get; set; } = null!;
+
+    public Sum()
+    {
+        _runJavaScript = new()
+        {
+            Script = new("getA() + getB();"),
+        };
+
+        Root = new Sequence
+        {
+            Activities =
+            {
+                _runJavaScript
+            }
+        };
+    }
+
+    protected override void ConfigureActivities(ActivityExecutionContext context)
+    {
+        // Copy input into variables so that JS activity can access them.
+        var a = A.Get(context);
+        var b = B.Get(context);
+        Variables.Add(new Variable<int>("A", a));
+        Variables.Add(new Variable<int>("B", b));
+
+        // If the call site set a result variable, assign it to the JavaScript activity's result.
+        if (Result != null)
+            _runJavaScript.Result = new(Result.MemoryBlockReference)!;
+    }
+}
+
+/// <summary>
+/// A workflow that uses the <see cref="Sum"/> composite activity.
+/// </summary>
+public class SumWorkflow : WorkflowBase
+{
+    protected override void Build(IWorkflowBuilder workflow)
+    {
+        var sum = workflow.WithVariable<int>("Sum", 0);
+
+        workflow.Root = new Sequence
+        {
+            Activities =
+            {
+                new Sum
+                {
+                    A = new(1),
+                    B = new(2),
+                    Result = new(sum)
+                },
+                new WriteLine(context => $"Sum: {sum.Get(context)}")
+            }
+        };
+    }
+}