Add a model corpus and characterization tests for the capability rules

app/Tests/Models/CorpusTests.cs

@@ -0,0 +1,68 @@
+using AIStudio.Provider;
+using AIStudio.Tests.Models.Corpus;
+
+namespace AIStudio.Tests.Models;
+
+/// <summary>
+/// Checks the corpus itself, before it is used to judge anything.
+/// </summary>
+/// <remarks>
+/// A ruler has to be straight before it can measure. A duplicate entry would silently outvote
+/// itself in the snapshot, and an entry which no longer belongs to any corpus model would make the
+/// list of known-wrong answers point at nothing.
+/// </remarks>
+[TestFixture]
+public sealed class CorpusTests
+{
+    [Test]
+    public void NoModelAppearsTwiceForTheSameProvider()
+    {
+        var duplicates = ModelCorpus.ENTRIES
+            .GroupBy(entry => (entry.Provider, entry.ModelId))
+            .Where(group => group.Count() > 1)
+            .Select(group => $"{group.Key.Provider} {group.Key.ModelId}")
+            .ToList();
+
+        Assert.That(duplicates, Is.Empty);
+    }
+
+    [Test]
+    public void EveryKnownWrongAnswerBelongsToAModelOfTheCorpus()
+    {
+        var corpus = ModelCorpus.ENTRIES.Select(entry => (entry.Provider, entry.ModelId)).ToHashSet();
+        var orphans = ExpectedChanges.ENTRIES
+            .Where(change => !corpus.Contains((change.Provider, change.ModelId)))
+            .Select(change => $"{change.Provider} {change.ModelId}")
+            .ToList();
+
+        Assert.That(orphans, Is.Empty);
+    }
+
+    [Test]
+    public void EveryKnownWrongAnswerSaysWhyAndWhereThatCanBeChecked()
+    {
+        Assert.Multiple(() =>
+        {
+            foreach (var change in ExpectedChanges.ENTRIES)
+            {
+                Assert.That(change.Reason, Is.Not.Empty, $"{change.Provider} {change.ModelId} does not say why the current answer is wrong.");
+                Assert.That(change.Source, Is.Not.Empty, $"{change.Provider} {change.ModelId} does not say where that can be checked.");
+                Assert.That(change.AnswerWanted, Is.Not.Empty, $"{change.Provider} {change.ModelId} does not say what the answer should be.");
+            }
+        });
+    }
+
+    [Test]
+    public void EveryProviderTheAppSupportsIsRepresented()
+    {
+        //
+        // A provider missing from the corpus is a whole branch of the dispatch nobody measures.
+        // That includes the ones without rules of their own: which rules they borrow, and what
+        // happens to the answer on the way back, is exactly the part a rebuild gets wrong.
+        //
+        var covered = ModelCorpus.ENTRIES.Select(entry => entry.Provider).ToHashSet();
+        var missing = Enum.GetValues<LLMProviders>().Where(provider => !covered.Contains(provider)).ToList();
+
+        Assert.That(missing, Is.Empty);
+    }
+}