part #2

src/__Tests/interop/StellaOps.Interop.Tests/FindingsComparer.cs

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+using System.Collections.Generic;
+using System.Linq;
+
+namespace StellaOps.Interop.Tests;
+
+public static class FindingsComparer
+{
+    public static FindingsComparisonResult Compare(
+        IReadOnlyList<Finding> stellaFindings,
+        IReadOnlyList<GrypeFinding> grypeFindings,
+        decimal tolerancePercent = 5)
+    {
+        var stellaVulns = stellaFindings
+            .Select(f => (f.VulnerabilityId, f.PackagePurl))
+            .ToHashSet();
+
+        var grypeVulns = grypeFindings
+            .Select(f => (f.VulnerabilityId, f.PackagePurl))
+            .ToHashSet();
+
+        var onlyInStella = stellaVulns.Except(grypeVulns).ToList();
+        var onlyInGrype = grypeVulns.Except(stellaVulns).ToList();
+        var inBoth = stellaVulns.Intersect(grypeVulns).ToList();
+
+        var totalUnique = stellaVulns.Union(grypeVulns).Count();
+        var parityPercent = totalUnique > 0
+            ? (decimal)inBoth.Count / totalUnique * 100
+            : 100;
+
+        return new FindingsComparisonResult(
+            ParityPercent: parityPercent,
+            IsWithinTolerance: parityPercent >= (100 - tolerancePercent),
+            StellaTotalFindings: stellaFindings.Count,
+            GrypeTotalFindings: grypeFindings.Count,
+            MatchingFindings: inBoth.Count,
+            OnlyInStella: onlyInStella.Count,
+            OnlyInGrype: onlyInGrype.Count,
+            OnlyInStellaDetails: onlyInStella,
+            OnlyInGrypeDetails: onlyInGrype);
+    }
+}