Refactor code structure for improved readability and maintainability; optimize performance in key functions.

src/Graph/__Tests/StellaOps.Graph.Api.Tests/LineageServiceTests.cs

@@ -0,0 +1,31 @@
+using System.Threading;
+using System.Threading.Tasks;
+using StellaOps.Graph.Api.Contracts;
+using StellaOps.Graph.Api.Services;
+using Xunit;
+
+namespace StellaOps.Graph.Api.Tests;
+
+public sealed class LineageServiceTests
+{
+    [Fact]
+    public async Task GetLineageAsync_ReturnsSbomAndArtifactChain()
+    {
+        var repository = new InMemoryGraphRepository();
+        var service = new InMemoryGraphLineageService(repository);
+
+        var request = new GraphLineageRequest
+        {
+            SbomDigest = "sha256:sbom-b",
+            MaxDepth = 3
+        };
+
+        var response = await service.GetLineageAsync("acme", request, CancellationToken.None);
+
+        Assert.Contains(response.Nodes, node => node.Id == "gn:acme:sbom:sha256:sbom-b");
+        Assert.Contains(response.Nodes, node => node.Id == "gn:acme:sbom:sha256:sbom-a");
+        Assert.Contains(response.Nodes, node => node.Id == "gn:acme:artifact:sha256:abc");
+        Assert.Contains(response.Edges, edge => edge.Kind == "SBOM_LINEAGE_PARENT");
+        Assert.Contains(response.Edges, edge => edge.Kind == "SBOM_VERSION_OF");
+    }
+}

src/Graph/__Tests/StellaOps.Graph.Indexer.Tests/SbomLineageTransformerTests.cs

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+using System;
+using System.Linq;
+using System.Text.Json.Nodes;
+using StellaOps.Graph.Indexer.Ingestion.Sbom;
+using Xunit;
+
+namespace StellaOps.Graph.Indexer.Tests;
+
+public sealed class SbomLineageTransformerTests
+{
+    [Fact]
+    public void Transform_adds_lineage_edges_when_present()
+    {
+        var snapshot = new SbomSnapshot
+        {
+            Tenant = "tenant-a",
+            ArtifactDigest = "sha256:artifact",
+            SbomDigest = "sha256:sbom",
+            SbomFormat = "cyclonedx",
+            SbomFormatVersion = "1.6",
+            Lineage = new[]
+            {
+                new SbomLineageReference
+                {
+                    Relationship = "parent",
+                    SbomDigest = "sha256:parent",
+                    ArtifactDigest = "sha256:parent-artifact",
+                    CollectedAt = DateTimeOffset.Parse("2025-12-01T00:00:00Z")
+                }
+            }
+        };
+
+        var transformer = new SbomIngestTransformer();
+        var batch = transformer.Transform(snapshot);
+
+        Assert.Contains(batch.Nodes, n => n["kind"]!.GetValue<string>() == "sbom");
+
+        var edgeKinds = batch.Edges
+            .Select(e => e["kind"]!.GetValue<string>())
+            .ToArray();
+
+        Assert.Contains("SBOM_VERSION_OF", edgeKinds);
+        Assert.Contains("SBOM_LINEAGE_PARENT", edgeKinds);
+    }
+}