chore: import upstream snapshot with attribution

dotnet/tests/Microsoft.Agents.AI.Foundry.UnitTests/ServedModelPolicyTests.cs

@@ -0,0 +1,84 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Threading.Tasks;
+using Microsoft.Extensions.AI;
+
+#pragma warning disable OPENAI001, MEAI001, MAAI001, SCME0001
+
+namespace Microsoft.Agents.AI.Foundry.UnitTests;
+
+/// <summary>
+/// Unit tests for <see cref="ServedModelPolicy"/>: the SCM pipeline policy that reads the
+/// <c>x-ms-served-model</c> response header and writes it into the active
+/// <see cref="ServedModelScope"/> box.
+/// </summary>
+/// <remarks>
+/// Tests drive the policy through a real OpenAI ResponsesClient SCM pipeline against a mock
+/// HTTP handler so the policy executes in its production configuration.
+/// </remarks>
+public sealed class ServedModelPolicyTests
+{
+    [Fact]
+    public void Instance_IsSingleton()
+    {
+        Assert.Same(ServedModelPolicy.Instance, ServedModelPolicy.Instance);
+    }
+
+    [Fact]
+    public async Task ProcessAsync_HeaderPresent_SetsModelIdOnResponseAsync()
+    {
+        // Arrange
+        using var handler = new ServedModelTestHelpers.ServedModelHandler(ServedModelTestHelpers.MinimalResponseJson(), servedModel: "gpt-5-nano-2025-08-07");
+        IChatClient chatClient = ServedModelTestHelpers.CreateChatClientWithPolicy(handler);
+
+        // Act
+        var response = await chatClient.GetResponseAsync("hi");
+
+        // Assert
+        Assert.Equal("gpt-5-nano-2025-08-07", response.ModelId);
+    }
+
+    [Fact]
+    public async Task ProcessAsync_HeaderAbsent_PreservesModelIdFromBodyAsync()
+    {
+        // Arrange
+        using var handler = new ServedModelTestHelpers.ServedModelHandler(ServedModelTestHelpers.MinimalResponseJson(), servedModel: null);
+        IChatClient chatClient = ServedModelTestHelpers.CreateChatClientWithPolicy(handler);
+
+        // Act
+        var response = await chatClient.GetResponseAsync("hi");
+
+        // Assert: ModelId is the deployment alias from the JSON body ("fake").
+        Assert.Equal("fake", response.ModelId);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("   ")]
+    public async Task ProcessAsync_EmptyOrWhitespaceHeader_PreservesModelIdFromBodyAsync(string headerValue)
+    {
+        // Arrange
+        using var handler = new ServedModelTestHelpers.ServedModelHandler(ServedModelTestHelpers.MinimalResponseJson(), servedModel: headerValue);
+        IChatClient chatClient = ServedModelTestHelpers.CreateChatClientWithPolicy(handler);
+
+        // Act
+        var response = await chatClient.GetResponseAsync("hi");
+
+        // Assert: empty/whitespace header is rejected by the policy, ModelId stays as "fake".
+        Assert.Equal("fake", response.ModelId);
+    }
+
+    [Fact]
+    public async Task ProcessAsync_HeaderWithSurroundingWhitespace_TrimsValueAsync()
+    {
+        // Arrange
+        using var handler = new ServedModelTestHelpers.ServedModelHandler(ServedModelTestHelpers.MinimalResponseJson(), servedModel: "  gpt-5-nano-2025-08-07  ");
+        IChatClient chatClient = ServedModelTestHelpers.CreateChatClientWithPolicy(handler);
+
+        // Act
+        var response = await chatClient.GetResponseAsync("hi");
+
+        // Assert
+        Assert.Equal("gpt-5-nano-2025-08-07", response.ModelId);
+    }
+}