Added some infrastructure and coverage for ASP.NET models

Would have allowed us to catch issues like dotnet/aspnetcore#12097

Part of #11838

Ideally, we should reference the actual "product" assemblies, but this requires changes to dependencies that I don't want to take on write now. #11838 is still open to track improvements.

I intend to add some more tests here before 3.0 to get some more coverage.

test/EFCore.InMemory.FunctionalTests/InMemoryComplianceTest.cs

@@ -16,6 +16,7 @@ public class InMemoryComplianceTest : ComplianceTestBase
             typeof(OptimisticConcurrencyTestBase<>),
             typeof(StoreGeneratedTestBase<>),
             typeof(LoadTestBase<>),                        // issue #15318
+            typeof(MusicStoreTestBase<>),                  // issue #15318
             typeof(GraphUpdatesTestBase<>),                // issue #15318
             typeof(ProxyGraphUpdatesTestBase<>),           // issue #15318
             typeof(ComplexNavigationsWeakQueryTestBase<>), // issue #15285

test/EFCore.InMemory.FunctionalTests/MusicStoreInMemoryTest.cs

@@ -0,0 +1,31 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.EntityFrameworkCore.TestUtilities;
+
+namespace Microsoft.EntityFrameworkCore
+{
+    // issue #15318
+    internal class MusicStoreInMemoryTest : MusicStoreTestBase<MusicStoreInMemoryTest.MusicStoreInMemoryFixture>
+    {
+        public MusicStoreInMemoryTest(MusicStoreInMemoryFixture fixture)
+            : base(fixture)
+        {
+        }
+
+        public class MusicStoreInMemoryFixture : MusicStoreFixtureBase
+        {
+            protected override ITestStoreFactory TestStoreFactory => InMemoryTestStoreFactory.Instance;
+
+            public override IDisposable BeginTransaction(DbContext context) => new InMemoryCleaner(context);
+
+            private class InMemoryCleaner : IDisposable
+            {
+                private readonly DbContext _context;
+                public InMemoryCleaner(DbContext context) => _context = context;
+                public void Dispose() => _context.Database.EnsureDeleted();
+            }
+        }
+    }
+}