Add tests for SBOM generation determinism across multiple formats

- Created `StellaOps.TestKit.Tests` project for unit tests related to determinism.
- Implemented `DeterminismManifestTests` to validate deterministic output for canonical bytes and strings, file read/write operations, and error handling for invalid schema versions.
- Added `SbomDeterminismTests` to ensure identical inputs produce consistent SBOMs across SPDX 3.0.1 and CycloneDX 1.6/1.7 formats, including parallel execution tests.
- Updated project references in `StellaOps.Integration.Determinism` to include the new determinism testing library.

src/Notify/__Tests/StellaOps.Notify.Storage.Postgres.Tests/NotifyPostgresFixture.cs

@@ -1,8 +1,19 @@
+// -----------------------------------------------------------------------------
+// NotifyPostgresFixture.cs
+// Sprint: SPRINT_5100_0007_0004_storage_harness
+// Task: STOR-HARNESS-012
+// Description: Notify PostgreSQL test fixture using TestKit
+// -----------------------------------------------------------------------------
+
 using System.Reflection;
 using StellaOps.Infrastructure.Postgres.Testing;
 using StellaOps.Notify.Storage.Postgres;
 using Xunit;
 
+// Type aliases to disambiguate TestKit and Infrastructure.Postgres.Testing fixtures
+using TestKitPostgresFixture = StellaOps.TestKit.Fixtures.PostgresFixture;
+using TestKitPostgresIsolationMode = StellaOps.TestKit.Fixtures.PostgresIsolationMode;
+
 namespace StellaOps.Notify.Storage.Postgres.Tests;
 
 /// <summary>
@@ -26,3 +37,36 @@ public sealed class NotifyPostgresCollection : ICollectionFixture<NotifyPostgres
 {
     public const string Name = "NotifyPostgres";
 }
+
+/// <summary>
+/// TestKit-based PostgreSQL fixture for Notify storage tests.
+/// Uses TestKit's PostgresFixture for enhanced isolation modes.
+/// </summary>
+public sealed class NotifyTestKitPostgresFixture : IAsyncLifetime
+{
+    private TestKitPostgresFixture _fixture = null!;
+    private Assembly MigrationAssembly => typeof(NotifyDataSource).Assembly;
+
+    public TestKitPostgresFixture Fixture => _fixture;
+    public string ConnectionString => _fixture.ConnectionString;
+
+    public async Task InitializeAsync()
+    {
+        _fixture = new TestKitPostgresFixture(TestKitPostgresIsolationMode.Truncation);
+        await _fixture.InitializeAsync();
+        await _fixture.ApplyMigrationsFromAssemblyAsync(MigrationAssembly);
+    }
+
+    public Task DisposeAsync() => _fixture.DisposeAsync();
+
+    public Task TruncateAllTablesAsync() => _fixture.TruncateAllTablesAsync();
+}
+
+/// <summary>
+/// Collection definition for Notify TestKit PostgreSQL tests.
+/// </summary>
+[CollectionDefinition(NotifyTestKitPostgresCollection.Name)]
+public sealed class NotifyTestKitPostgresCollection : ICollectionFixture<NotifyTestKitPostgresFixture>
+{
+    public const string Name = "NotifyTestKitPostgres";
+}

src/Notify/__Tests/StellaOps.Notify.Storage.Postgres.Tests/StellaOps.Notify.Storage.Postgres.Tests.csproj

@@ -29,6 +29,6 @@
   <ItemGroup>
     <ProjectReference Include="..\..\__Libraries\StellaOps.Notify.Storage.Postgres\StellaOps.Notify.Storage.Postgres.csproj" />
     <ProjectReference Include="..\..\..\__Libraries\StellaOps.Infrastructure.Postgres.Testing\StellaOps.Infrastructure.Postgres.Testing.csproj" />
+    <ProjectReference Include="..\..\..\__Libraries\StellaOps.TestKit\StellaOps.TestKit.csproj" />
   </ItemGroup>
-
 </Project>