Add a model corpus and characterization tests for the capability rules

app/Tests/Models/SnapshotWriterTests.cs

@@ -0,0 +1,29 @@
+using AIStudio.Tests.Models.Corpus;
+
+namespace AIStudio.Tests.Models;
+
+/// <summary>
+/// Writes the capability snapshot anew.
+/// </summary>
+/// <remarks>
+/// Marked explicit, so it never runs as part of the suite: it would make the characterization test
+/// pass by rewriting what that test compares against. Run it by hand, from the IDE or with
+/// "dotnet test --filter TakeTheSnapshotAnew", once a diff has been read and accepted, and commit
+/// the new file together with the change which caused it.
+/// </remarks>
+[TestFixture]
+[Explicit("Rewrites the file the characterization test compares against. Run it only after reading the diff.")]
+public sealed class SnapshotWriterTests
+{
+    [Test]
+    public void TakeTheSnapshotAnew()
+    {
+        var knownWrong = ExpectedChanges.ENTRIES.Select(change => (change.Provider, change.ModelId)).ToHashSet();
+        var entries = ModelCorpus.ENTRIES.Where(entry => !knownWrong.Contains((entry.Provider, entry.ModelId)));
+
+        File.WriteAllText(CapabilitySnapshot.FILE_PATH, CapabilitySnapshot.Render(entries));
+        File.Delete(CapabilitySnapshot.ACTUAL_FILE_PATH);
+
+        TestContext.Out.WriteLine($"Wrote {CapabilitySnapshot.FILE_PATH}. Read the diff before committing it.");
+    }
+}