test: qualify native MEAI instructions streaming

Author: KSemenenko

CodexSharpSDK.Tests/Integration/RealCodexIntegrationTests.cs

@@ -1,14 +1,55 @@
+using System.Text;
 using System.Text.Json.Nodes;
 using ManagedCode.CodexSharpSDK.Client;
 using ManagedCode.CodexSharpSDK.Configuration;
+using ManagedCode.CodexSharpSDK.Extensions.AI;
 using ManagedCode.CodexSharpSDK.Models;
 using ManagedCode.CodexSharpSDK.Tests.Shared;
+using Microsoft.Extensions.AI;
 
 namespace ManagedCode.CodexSharpSDK.Tests.Integration;
 
 [Property("RequiresCodexAuth", "true")]
 public class RealCodexIntegrationTests
 {
+    private const string InstructionsAnswer = "native-meai-instructions-confirmed";
+    private const string NativeInstructions = "Reply with exactly native-meai-instructions-confirmed. Do not use tools, execute commands or change files.";
+    private const string NativeUserPrompt = "Return the exact answer specified by your system instructions.";
+
+    [Test]
+    public async Task GetStreamingResponseAsync_WithRealCodexCli_HonorsStandardInstructions()
+    {
+        using var settings = RealCodexTestSupport.GetRequiredSettings();
+        using var client = new CodexChatClient(new CodexChatClientOptions
+        {
+            CodexOptions = new CodexOptions { EnvironmentVariables = settings.EnvironmentOverrides },
+            DefaultModel = settings.Model,
+            DefaultThreadOptions = new ThreadOptions
+            {
+                Model = settings.Model,
+                WebSearchMode = WebSearchMode.Disabled,
+                SandboxMode = SandboxMode.ReadOnly,
+                NetworkAccessEnabled = true,
+            },
+        });
+        using var cancellation = new CancellationTokenSource(TimeSpan.FromMinutes(2));
+        var text = new StringBuilder();
+        var hasUsage = false;
+        var hasTerminal = false;
+        await foreach (var update in client.GetStreamingResponseAsync(
+            [new ChatMessage(ChatRole.User, NativeUserPrompt)],
+            new ChatOptions { Instructions = NativeInstructions },
+            cancellation.Token))
+        {
+            text.Append(update.Text);
+            hasUsage |= update.Contents.OfType<UsageContent>().Any();
+            hasTerminal |= update.FinishReason is not null;
+        }
+        await Assert.That(text.ToString().Trim()).IsEqualTo(InstructionsAnswer);
+        await Assert.That(hasUsage).IsTrue();
+        await Assert.That(hasTerminal).IsTrue();
+    }
+
     [Test]
     public async Task RunAsync_WithRealCodexCli_ReturnsStructuredOutput()
     {