Added the guided chat to the BeyondFacts Lab (#1177)

app/Tests/BeyondFactsLab/BflTokenBudgetTests.cs

@@ -0,0 +1,49 @@
+using AIStudio.Assistants.BeyondFactsLab;
+using AIStudio.Chat;
+using AIStudio.Models;
+
+namespace AIStudio.Tests.BeyondFactsLab;
+
+/// <summary>
+/// Checks when the BeyondFacts Lab warns about a full context, and when it stops sending.
+/// </summary>
+[TestFixture]
+public sealed class BflTokenBudgetTests
+{
+    private const int WINDOW = 32_000;
+
+    [Test]
+    public void ACountWhichFailedTellsNothing()
+    {
+        Assert.That(BflTokenBudget.Of(ConversationTokens.UNAVAILABLE), Is.EqualTo(BflTokenBudgetState.UNKNOWN));
+    }
+
+    [Test]
+    public void AModelWithoutAStatementAboutItsWindowTellsNothing()
+    {
+        var tokens = new ConversationTokens { IsKnown = true, HistoryTokens = 500_000, Window = ContextWindow.UNKNOWN };
+
+        Assert.That(BflTokenBudget.Of(tokens), Is.EqualTo(BflTokenBudgetState.UNKNOWN), "The lab cannot know when such a model is full, so it never stops sending.");
+    }
+
+    [TestCase(0, BflTokenBudgetState.OK)]
+    [TestCase(25_599, BflTokenBudgetState.OK)]
+    [TestCase(25_600, BflTokenBudgetState.WARNING)]
+    [TestCase(WINDOW - BflTokenBudget.RESERVE_TOKENS, BflTokenBudgetState.WARNING)]
+    [TestCase(WINDOW - BflTokenBudget.RESERVE_TOKENS + 1, BflTokenBudgetState.FULL)]
+    [TestCase(WINDOW * 2, BflTokenBudgetState.FULL)]
+    public void TheShareOfTheWindowDecides(int historyTokens, BflTokenBudgetState expected)
+    {
+        var tokens = new ConversationTokens { IsKnown = true, HistoryTokens = historyTokens, Window = ContextWindow.Of(WINDOW) };
+
+        Assert.That(BflTokenBudget.Of(tokens), Is.EqualTo(expected));
+    }
+
+    [Test]
+    public void TheMessageBeingWrittenCountsAsWell()
+    {
+        var tokens = new ConversationTokens { IsKnown = true, HistoryTokens = 20_000, DraftTokens = 6_000, Window = ContextWindow.Of(WINDOW) };
+
+        Assert.That(BflTokenBudget.Of(tokens), Is.EqualTo(BflTokenBudgetState.WARNING));
+    }
+}