Add header propagation tests

Author: ceciliaavila

libraries/Microsoft.Bot.Connector/HeaderPropagationEntryCollection.cs

@@ -49,10 +49,18 @@ public void Add(string key, StringValues value)
         /// <param name="value">The value to append for the specified key.</param>
         public void Append(string key, StringValues value)
         {
+            StringValues newValue;
+
+            if (_entries.TryGetValue(key, out var entry))
+            {
+                // If the key already exists, append the new value to the existing one.
+                newValue = StringValues.Concat(entry.Value, value);
+            }
+
             _entries[key] = new HeaderPropagationEntry
             {
                 Key = key,
-                Value = value,
+                Value = !StringValues.IsNullOrEmpty(newValue) ? newValue : value,
                 Action = HeaderPropagationEntryAction.Append
             };
         }

tests/Microsoft.Bot.Connector.Tests/HeaderPropagationTests.cs

@@ -0,0 +1,116 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Collections.Generic;
+using Microsoft.Extensions.Primitives;
+using Xunit;
+
+namespace Microsoft.Bot.Connector.Tests
+{
+    [Collection("Non-Parallel Collection")] // Ensure this test runs in a single-threaded context to avoid issues with static dictionary.
+    public class HeaderPropagationTests
+    {
+        public HeaderPropagationTests()
+        {
+            HeaderPropagation.HeadersToPropagate = new Dictionary<string, StringValues>();
+        }
+
+        [Fact]
+        public void HeaderPropagationContext_ShouldFilterHeaders()
+        {
+            // Arrange
+            HeaderPropagation.RequestHeaders = new Dictionary<string, StringValues>
+            {
+                { "x-custom-header-1", new StringValues("Value-1") },
+                { "x-custom-header-2", new StringValues("Value-2") },
+                { "x-custom-header-3", new StringValues("Value-3") }
+            };
+
+            var headersToPropagate = new HeaderPropagationEntryCollection();
+
+            headersToPropagate.Add("x-custom-header", "custom-value");
+            headersToPropagate.Propagate("x-custom-header-1");
+            headersToPropagate.Override("x-custom-header-2", "new-value");
+            headersToPropagate.Append("x-custom-header-3", "extra-value");
+
+            // Act
+            var filteredHeaders = HeaderPropagation.FilterHeaders(headersToPropagate);
+
+            // Assert
+            Assert.Equal(4, filteredHeaders.Count);
+            Assert.Equal("custom-value", filteredHeaders["x-custom-header"]);
+            Assert.Equal("Value-1", filteredHeaders["x-custom-header-1"]);
+            Assert.Equal("new-value", filteredHeaders["x-custom-header-2"]);
+            Assert.Equal("Value-3,extra-value", filteredHeaders["x-custom-header-3"]);
+        }
+
+        [Fact]
+        public void HeaderPropagationContext_ShouldAppendMultipleValues()
+        {
+            // Arrange
+            HeaderPropagation.RequestHeaders = new Dictionary<string, StringValues>
+            {
+                { "User-Agent", new StringValues("Value-1") }
+            };
+
+            var headersToPropagate = new HeaderPropagationEntryCollection();
+
+            headersToPropagate.Append("User-Agent", "extra-value-1");
+            headersToPropagate.Append("User-Agent", "extra-value-2");
+
+            // Act
+            var filteredHeaders = HeaderPropagation.FilterHeaders(headersToPropagate);
+
+            // Assert
+            Assert.Single(filteredHeaders);
+            Assert.Equal("Value-1,extra-value-1,extra-value-2", filteredHeaders["User-Agent"]);
+        }
+
+        [Fact]
+        public void HeaderPropagationContext_MultipleAdd_ShouldKeepLastValue()
+        {
+            // Arrange
+            HeaderPropagation.RequestHeaders = new Dictionary<string, StringValues>();
+            
+            var headersToPropagate = new HeaderPropagationEntryCollection();
+
+            headersToPropagate.Add("x-custom-header-1", "value-1");
+            headersToPropagate.Add("x-custom-header-1", "value-2");
+
+            // Act
+            var filteredHeaders = HeaderPropagation.FilterHeaders(headersToPropagate);
+
+            // Assert
+            Assert.Single(filteredHeaders);
+            Assert.Equal("value-2", filteredHeaders["x-custom-header-1"]);
+        }
+
+        [Fact]
+        public void HeaderPropagationContext_MultipleOverride_ShouldKeepLastValue()
+        {
+            // Arrange
+            HeaderPropagation.RequestHeaders = new Dictionary<string, StringValues>
+            {
+                { "x-custom-header-1", new StringValues("Value-1") }
+            };
+
+            var headersToPropagate = new HeaderPropagationEntryCollection();
+            headersToPropagate.Override("x-custom-header-1", "new-value-1");
+            headersToPropagate.Override("x-custom-header-1", "new-value-2");
+
+            // Act
+            var filteredHeaders = HeaderPropagation.FilterHeaders(headersToPropagate);
+
+            // Assert
+            Assert.Single(filteredHeaders);
+            Assert.Equal("new-value-2", filteredHeaders["x-custom-header-1"]);
+        }
+    }
+
+    [CollectionDefinition("Non-Parallel Collection", DisableParallelization = true)]
+#pragma warning disable SA1402 // File may only contain a single type
+    public class NonParallelCollectionDefinition 
+    {
+    }
+#pragma warning restore SA1402 // File may only contain a single type
+}