Added the Model Comparison assistant for blind comparisons of two models (#1009)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/Tests/Assistants/ModelComparison/ModelComparisonProviderAdapterTests.cs

@@ -0,0 +1,58 @@
+using AIStudio.Assistants.ModelComparison;
+using AIStudio.Provider;
+using AIStudio.Settings;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Abstractions;
+
+namespace AIStudio.Tests.Assistants.ModelComparison;
+
+/// <summary>
+/// Checks that the model comparison asks a provider only when every chat of the app would ask it.
+/// </summary>
+/// <remarks>
+/// The settings are reached through Program.SERVICE_PROVIDER, as in the app, because the check of a chat
+/// reads them from there, see ProhibitedProvidersTests.
+/// </remarks>
+[TestFixture]
+public sealed class ModelComparisonProviderAdapterTests
+{
+    private SettingsManager settingsManager = null!;
+    private ServiceProvider serviceProvider = null!;
+    private IServiceProvider previousServiceProvider = null!;
+
+    [SetUp]
+    public void CreateSettings()
+    {
+        this.settingsManager = new SettingsManager(NullLogger<SettingsManager>.Instance, null!);
+
+        this.previousServiceProvider = Program.SERVICE_PROVIDER;
+        this.serviceProvider = new ServiceCollection().AddSingleton(this.settingsManager).BuildServiceProvider();
+        Program.SERVICE_PROVIDER = this.serviceProvider;
+    }
+
+    [TearDown]
+    public void RestoreApplicationState()
+    {
+        Program.SERVICE_PROVIDER = this.previousServiceProvider;
+        this.serviceProvider.Dispose();
+    }
+
+    [Test]
+    public async Task AProviderWhichTheOrganizationProhibitedIsNotAsked()
+    {
+        var provider = new AIStudio.Settings.Provider(1, Guid.NewGuid().ToString(), "Instance 1", LLMProviders.DEEP_SEEK, new("test-model", null));
+        var participant = ModelComparisonProviderAdapter.CreateParticipant(provider, this.settingsManager, AIStudio.Tools.Components.MODEL_COMPARISON_ASSISTANT, "Model Comparison");
+
+        // Prohibited after it was selected, as an organization may do at any time:
+        this.settingsManager.ConfigurationData.App.ProhibitedProviders.Add(LLMProviders.DEEP_SEEK);
+
+        // Thrown before any request leaves the app; the runner turns it into a model which did not answer:
+        await Assert.ThrowsAsync<InvalidOperationException>(async () =>
+        {
+            await foreach (var _ in participant.Ask("A question.", CancellationToken.None))
+            {
+            }
+        });
+    }
+}