Rebuilt how AI Studio knows what a model can do (#960)

app/Tests/Provider/HFModelTests.cs

@@ -0,0 +1,95 @@
+using AIStudio.Provider.HuggingFace;
+
+namespace AIStudio.Tests.Provider;
+
+/// <summary>
+/// Checks which window a model has when it is reached through the Hugging Face router.
+/// </summary>
+/// <remarks>
+/// The router is the one provider where the window does not belong to the model: the same weights
+/// run behind several inference providers, each configured by somebody else, and which of them
+/// answers depends on what the user chose.
+/// </remarks>
+[TestFixture]
+public sealed class HFModelTests
+{
+    private const string AUTOMATIC = "";
+
+    private static readonly HFModel SERVED_BY_THREE = new("deepseek-ai/DeepSeek-R1",
+    [
+        new("novita", "live", 64_000),
+        new("together", "live", 128_000),
+        new("fireworks-ai", "live", 160_000),
+    ]);
+
+    [Test]
+    public void AChosenProviderAnswersForItself()
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(SERVED_BY_THREE.ContextWindowTokens("novita"), Is.EqualTo(64_000));
+            Assert.That(SERVED_BY_THREE.ContextWindowTokens("together"), Is.EqualTo(128_000));
+        });
+    }
+
+    [Test]
+    public void AChosenProviderIsFoundHoweverItIsSpelled()
+    {
+        Assert.That(SERVED_BY_THREE.ContextWindowTokens("Novita"), Is.EqualTo(64_000));
+    }
+
+    [Test]
+    public void LettingTheRouterChooseMeansTheSmallestWindowOnOffer()
+    {
+        //
+        // Nobody knows which provider the router will take. Promising the largest window would walk
+        // a conversation into an error the user could not see coming; the smallest one only warns
+        // them earlier than strictly necessary.
+        //
+        Assert.That(SERVED_BY_THREE.ContextWindowTokens(AUTOMATIC), Is.EqualTo(64_000));
+    }
+
+    [Test]
+    public void AProviderWhichIsNotServingDoesNotDecideAnything()
+    {
+        var oneIsDown = new HFModel("deepseek-ai/DeepSeek-R1",
+        [
+            new("novita", "staging", 8_000),
+            new("together", "live", 128_000),
+        ]);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(oneIsDown.ContextWindowTokens(AUTOMATIC), Is.EqualTo(128_000), "The small window belongs to a provider nobody can reach.");
+            Assert.That(oneIsDown.ContextWindowTokens("novita"), Is.Null, "And asking for that provider by name does not bring it back either.");
+        });
+    }
+
+    [Test]
+    public void AProviderWhichDoesNotServeTheModelSaysNothingAboutIt()
+    {
+        Assert.That(SERVED_BY_THREE.ContextWindowTokens("cerebras"), Is.Null);
+    }
+
+    [Test]
+    public void AWindowNobodyStatedIsSkippedRatherThanCountedAsNothing()
+    {
+        var halfStated = new HFModel("deepseek-ai/DeepSeek-R1",
+        [
+            new("novita", "live", null),
+            new("together", "live", 128_000),
+        ]);
+
+        Assert.That(halfStated.ContextWindowTokens(AUTOMATIC), Is.EqualTo(128_000), "A missing number is not the smallest number.");
+    }
+
+    [Test]
+    public void AModelNobodyServesHasNoWindow()
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(new HFModel("org/model", null).ContextWindowTokens(AUTOMATIC), Is.Null);
+            Assert.That(new HFModel("org/model", []).ContextWindowTokens(AUTOMATIC), Is.Null);
+        });
+    }
+}