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/ModelComparisonShownChatTests.cs

@@ -0,0 +1,61 @@
+using AIStudio.Assistants.ModelComparison;
+using AIStudio.Provider;
+
+namespace AIStudio.Tests.Assistants.ModelComparison;
+
+/// <summary>
+/// Checks which chat of a task the user works in, which model answers there, and whether it starts with the first
+/// message of the first chat.
+/// </summary>
+[TestFixture]
+public sealed class ModelComparisonShownChatTests
+{
+    private static readonly DateTimeOffset BEGUN = new(2026, 11, 13, 9, 0, 0, TimeSpan.Zero);
+
+    private static readonly AIStudio.Settings.Provider FIRST_PROVIDER = new(0, "11111111-1111-1111-1111-111111111111", "First", LLMProviders.OPEN_AI, new Model("model-a", null));
+
+    private static readonly AIStudio.Settings.Provider SECOND_PROVIDER = new(1, "22222222-2222-2222-2222-222222222222", "Second", LLMProviders.MISTRAL, new Model("model-b", null));
+
+    [TestCase(true, "First")]
+    [TestCase(false, "Second")]
+    public void TheFirstChatHasTheModelDrawnForItAndNoOpeningMessage(bool firstModelIsChatOne, string expectedProvider)
+    {
+        var task = ModelComparisonSeriesTask.Begin(BEGUN, firstModelIsChatOne);
+        var chat = ModelComparisonShownChat.Of(task, FIRST_PROVIDER, SECOND_PROVIDER);
+
+        Assert.That(chat, Is.Not.Null);
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(chat!.ChatId, Is.EqualTo(task.ChatOne.ChatId));
+            Assert.That(chat.Provider.InstanceName, Is.EqualTo(expectedProvider));
+            Assert.That(chat.OpensWithFirstMessage, Is.False, "The first chat starts with whatever the user writes.");
+        }
+    }
+
+    [TestCase(true, "Second")]
+    [TestCase(false, "First")]
+    public void TheSecondChatHasTheOtherModelAndStartsWithTheFirstMessage(bool firstModelIsChatOne, string expectedProvider)
+    {
+        var task = ModelComparisonSeriesTask.Begin(BEGUN, firstModelIsChatOne);
+        task.FinishFirstChat(BEGUN.AddMinutes(1), BEGUN.AddMinutes(5), 1, "What is new today?");
+        var chat = ModelComparisonShownChat.Of(task, FIRST_PROVIDER, SECOND_PROVIDER);
+
+        Assert.That(chat, Is.Not.Null);
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(chat!.ChatId, Is.EqualTo(task.ChatTwo.ChatId));
+            Assert.That(chat.Provider.InstanceName, Is.EqualTo(expectedProvider), "The second chat must never go to the model of the first one.");
+            Assert.That(chat.OpensWithFirstMessage, Is.True, "Without the first message, the second model would never answer the task.");
+        }
+    }
+
+    [Test]
+    public void ATaskWaitingForTheDecisionShowsNoChat()
+    {
+        var task = ModelComparisonSeriesTask.Begin(BEGUN, firstModelIsChatOne: true);
+        task.FinishFirstChat(BEGUN.AddMinutes(1), BEGUN.AddMinutes(5), 1, "What is new today?");
+        task.FinishSecondChat(BEGUN.AddMinutes(6), BEGUN.AddMinutes(9), 1);
+
+        Assert.That(ModelComparisonShownChat.Of(task, FIRST_PROVIDER, SECOND_PROVIDER), Is.Null);
+    }
+}