sprints and audit work

src/Policy/__Tests/StellaOps.Policy.Tests/Gates/FacetQuotaGateTests.cs

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+// <copyright file="FacetQuotaGateTests.cs" company="StellaOps">
+// Copyright (c) StellaOps. Licensed under AGPL-3.0-or-later.
+// </copyright>
+// Sprint: SPRINT_20260105_002_003_FACET (QTA-014)
+
+using System.Collections.Immutable;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using StellaOps.Facet;
+using StellaOps.Policy.Confidence.Models;
+using StellaOps.Policy.Gates;
+using StellaOps.Policy.TrustLattice;
+using Xunit;
+
+namespace StellaOps.Policy.Tests.Gates;
+
+/// <summary>
+/// Unit tests for <see cref="FacetQuotaGate"/> evaluation scenarios.
+/// </summary>
+[Trait("Category", "Unit")]
+public sealed class FacetQuotaGateTests
+{
+    private readonly Mock<IFacetDriftDetector> _driftDetectorMock;
+    private readonly FacetQuotaGateOptions _options;
+    private FacetQuotaGate _gate;
+
+    public FacetQuotaGateTests()
+    {
+        _driftDetectorMock = new Mock<IFacetDriftDetector>();
+        _options = new FacetQuotaGateOptions { Enabled = true };
+        _gate = CreateGate(_options);
+    }
+
+    private FacetQuotaGate CreateGate(FacetQuotaGateOptions options)
+    {
+        return new FacetQuotaGate(options, _driftDetectorMock.Object, NullLogger<FacetQuotaGate>.Instance);
+    }
+
+    [Fact]
+    public async Task EvaluateAsync_WhenDisabled_ReturnsPass()
+    {
+        // Arrange
+        var options = new FacetQuotaGateOptions { Enabled = false };
+        var gate = CreateGate(options);
+        var context = CreateContext();
+        var mergeResult = CreateMergeResult();
+
+        // Act
+        var result = await gate.EvaluateAsync(mergeResult, context);
+
+        // Assert
+        Assert.True(result.Passed);
+        Assert.Equal("Gate disabled", result.Reason);
+    }
+
+    [Fact]
+    public async Task EvaluateAsync_WhenNoSealAndNoSealActionIsPass_ReturnsPass()
+    {
+        // Arrange - no drift report in context means no seal
+        var options = new FacetQuotaGateOptions { Enabled = true, NoSealAction = NoSealAction.Pass };
+        var gate = CreateGate(options);
+        var context = CreateContext();
+        var mergeResult = CreateMergeResult();
+
+        // Act
+        var result = await gate.EvaluateAsync(mergeResult, context);
+
+        // Assert
+        Assert.True(result.Passed);
+        Assert.Contains("first scan", result.Reason);
+    }
+
+    [Fact]
+    public async Task EvaluateAsync_WhenNoSealAndNoSealActionIsWarn_ReturnsPassWithWarning()
+    {
+        // Arrange
+        var options = new FacetQuotaGateOptions { Enabled = true, NoSealAction = NoSealAction.Warn };
+        var gate = CreateGate(options);
+        var context = CreateContext();
+        var mergeResult = CreateMergeResult();
+
+        // Act
+        var result = await gate.EvaluateAsync(mergeResult, context);
+
+        // Assert
+        Assert.True(result.Passed);
+        Assert.Equal("no_baseline_seal", result.Reason);
+        Assert.True(result.Details.ContainsKey("action"));
+    }
+
+    [Fact]
+    public async Task EvaluateAsync_WhenNoSealAndNoSealActionIsBlock_ReturnsFail()
+    {
+        // Arrange
+        var options = new FacetQuotaGateOptions { Enabled = true, NoSealAction = NoSealAction.Block };
+        var gate = CreateGate(options);
+        var context = CreateContext();
+        var mergeResult = CreateMergeResult();
+
+        // Act
+        var result = await gate.EvaluateAsync(mergeResult, context);
+
+        // Assert
+        Assert.False(result.Passed);
+        Assert.Equal("no_baseline_seal", result.Reason);
+    }
+
+    [Fact]
+    public async Task EvaluateAsync_NullMergeResult_ThrowsArgumentNullException()
+    {
+        // Arrange
+        var context = CreateContext();
+
+        // Act & Assert
+        await Assert.ThrowsAsync<ArgumentNullException>(() =>
+            _gate.EvaluateAsync(null!, context));
+    }
+
+    [Fact]
+    public async Task EvaluateAsync_NullContext_ThrowsArgumentNullException()
+    {
+        // Arrange
+        var mergeResult = CreateMergeResult();
+
+        // Act & Assert
+        await Assert.ThrowsAsync<ArgumentNullException>(() =>
+            _gate.EvaluateAsync(mergeResult, null!));
+    }
+
+    private static PolicyGateContext CreateContext()
+    {
+        return new PolicyGateContext
+        {
+            Environment = "test"
+        };
+    }
+
+    private static PolicyGateContext CreateContextWithDriftReportJson(string driftReportJson)
+    {
+        return new PolicyGateContext
+        {
+            Environment = "test",
+            Metadata = new Dictionary<string, string>
+            {
+                ["FacetDriftReport"] = driftReportJson
+            }
+        };
+    }
+
+    private static MergeResult CreateMergeResult()
+    {
+        var emptyClaim = new ScoredClaim
+        {
+            SourceId = "test",
+            Status = VexStatus.NotAffected,
+            OriginalScore = 1.0,
+            AdjustedScore = 1.0,
+            ScopeSpecificity = 1,
+            Accepted = true,
+            Reason = "test"
+        };
+
+        return new MergeResult
+        {
+            Status = VexStatus.NotAffected,
+            Confidence = 0.9,
+            HasConflicts = false,
+            AllClaims = [emptyClaim],
+            WinningClaim = emptyClaim,
+            Conflicts = []
+        };
+    }
+
+    private static FacetDriftReport CreateDriftReport(QuotaVerdict verdict)
+    {
+        return new FacetDriftReport
+        {
+            ImageDigest = "sha256:abc123",
+            BaselineSealId = "seal-123",
+            AnalyzedAt = DateTimeOffset.UtcNow,
+            FacetDrifts = [CreateFacetDrift("test-facet", verdict)],
+            OverallVerdict = verdict
+        };
+    }
+
+    private static FacetDrift CreateFacetDrift(
+        string facetId,
+        QuotaVerdict verdict,
+        int baselineFileCount = 100)
+    {
+        // ChurnPercent is computed from TotalChanges / BaselineFileCount
+        // For different verdicts, we add files appropriately
+        var addedCount = verdict switch
+        {
+            QuotaVerdict.Warning => 10, // 10% churn
+            QuotaVerdict.Blocked => 30, // 30% churn
+            QuotaVerdict.RequiresVex => 50, // 50% churn
+            _ => 0
+        };
+
+        var addedFiles = Enumerable.Range(0, addedCount)
+            .Select(i => new FacetFileEntry(
+                $"/added/file{i}.txt",
+                $"sha256:added{i}",
+                100,
+                null))
+            .ToImmutableArray();
+
+        return new FacetDrift
+        {
+            FacetId = facetId,
+            Added = addedFiles,
+            Removed = [],
+            Modified = [],
+            DriftScore = addedCount,
+            QuotaVerdict = verdict,
+            BaselineFileCount = baselineFileCount
+        };
+    }
+}