@@ -0,0 +1,188 @@
+using System.Text.Json;
+using Xunit;
+
+public sealed class PimaxUsbEnumerationTests
+{
+    [Fact]
+    public void EmptyInventorySerializesRequiredSchemaAndFields()
+    {
+        var snapshot = new PimaxUsbEnumerationSnapshotCollector(new FakeInventorySource([])).Collect();
+        var json = JsonSerializer.Serialize(snapshot, PimaxUsbEnumerationJson.Options);
+
+        Assert.Equal(PimaxUsbEnumerationSchema.Version, snapshot.SchemaVersion);
+        Assert.Equal(0, snapshot.InventorySummary.TotalDevices);
+        Assert.Empty(snapshot.CandidateDevices);
+        Assert.Contains("\"schemaVersion\":\"pimax-usb-enumeration-v1\"", json);
+        Assert.Contains("\"inventorySummary\"", json);
+        Assert.Contains("\"candidateDevices\"", json);
+        Assert.Contains("\"fullInventory\"", json);
+        Assert.Contains("\"warnings\"", json);
+        Assert.Contains("\"errors\"", json);
+    }
+
+    [Fact]
+    public void IdentitySanitizerIsDeterministicAndDoesNotExposeRawSerial()
+    {
+        const string first = @"USB\VID_34A4&PID_0012\P30100P201382100320";
+        const string second = @"USB\VID_34A4&PID_0012\DIFFERENT";
+
+        var firstHash = PnpIdentitySanitizer.StableHash(first);
+        var repeatedHash = PnpIdentitySanitizer.StableHash(first.ToLowerInvariant());
+        var secondHash = PnpIdentitySanitizer.StableHash(second);
+
+        Assert.Equal(firstHash, repeatedHash);
+        Assert.NotEqual(firstHash, secondHash);
+        Assert.DoesNotContain("P30100P201382100320", firstHash, StringComparison.OrdinalIgnoreCase);
+        Assert.StartsWith("sha256:", firstHash);
+        Assert.Null(PnpIdentitySanitizer.StableHashOrNull(null));
+    }
+
+    [Fact]
+    public void KnownCrystalVidPidSelectsCandidateWithoutRawIdentifierLeak()
+    {
+        var raw = Raw(instanceId: @"USB\VID_34A4&PID_0012\P30100P201382100320", deviceClass: "USB");
+        var snapshot = new PimaxUsbEnumerationSnapshotCollector(new FakeInventorySource([raw])).Collect();
+        var candidate = Assert.Single(snapshot.CandidateDevices);
+        var json = JsonSerializer.Serialize(snapshot, PimaxUsbEnumerationJson.Options);
+
+        Assert.Contains("knownCrystalVidPid", candidate.CandidateReasons);
+        Assert.Contains("usbDeviceWithRelevantInterfaceClass", candidate.CandidateReasons);
+        Assert.Equal("34A4", candidate.Vid);
+        Assert.Equal("0012", candidate.Pid);
+        Assert.DoesNotContain("P30100P201382100320", json, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void CandidateSelectionUsesNameInterfaceAndProblemEvidence()
+    {
+        var raw = Raw(
+            instanceId: @"HID\VID_9999&PID_8888\FAKE123",
+            deviceClass: "HIDClass",
+            friendlyName: "Pimax Controller Interface",
+            problemCode: 28,
+            status: "Problem");
+
+        var candidate = Assert.Single(new PimaxUsbEnumerationSnapshotCollector(new FakeInventorySource([raw])).Collect().CandidateDevices);
+
+        Assert.Contains("knownPimaxName", candidate.CandidateReasons);
+        Assert.Contains("relatedHidInterface", candidate.CandidateReasons);
+        Assert.Contains("problemUsbOrPnpDevice", candidate.CandidateReasons);
+        Assert.Equal(28, candidate.ProblemCode);
+    }
+
+    [Fact]
+    public void SummaryCountsPresentNonPresentProblemDuplicateRows()
+    {
+        var devices = new[]
+        {
+            Raw(instanceId: @"USB\VID_34A4&PID_0012\ONE", deviceClass: "USB"),
+            Raw(instanceId: @"USB\VID_34A4&PID_0012\ONE", deviceClass: "USB"),
+            Raw(instanceId: @"USB\VID_34A4&PID_0012\TWO", deviceClass: "USB", present: false, phantom: true, connected: false, status: "NonPresent"),
+            Raw(instanceId: @"USB\VID_34A4&PID_0012\THREE", deviceClass: "USB", problemCode: 10, status: "Problem")
+        };
+
+        var summary = new PimaxUsbEnumerationSnapshotCollector(new FakeInventorySource(devices)).Collect().InventorySummary;
+
+        Assert.Equal(4, summary.TotalDevices);
+        Assert.Equal(3, summary.PresentDevices);
+        Assert.Equal(1, summary.NonPresentDevices);
+        Assert.Equal(1, summary.ProblemDevices);
+        Assert.Equal(4, summary.CountsByEnumerator["USB"]);
+        Assert.Equal(4, summary.CountsByVidPid["VID_34A4&PID_0012"]);
+    }
+
+    [Fact]
+    public void ParentContainerAndLocationPathsAreSanitizedButStable()
+    {
+        var raw = Raw(
+            instanceId: @"USB\VID_34A4&PID_0012\CHILD",
+            parentInstanceId: @"USB\ROOT_HUB30\ROOTSERIAL",
+            containerId: "{11111111-2222-3333-4444-555555555555}",
+            locationPaths: [@"PCIROOT(0)#PCI(1400)#USBROOT(0)#USB(3)"]);
+
+        var record = Assert.Single(new PimaxUsbEnumerationSnapshotCollector(new FakeInventorySource([raw])).Collect().FullInventory);
+
+        Assert.NotNull(record.ParentStableId);
+        Assert.NotNull(record.ContainerStableId);
+        Assert.Single(record.LocationPathHashes);
+        Assert.DoesNotContain("ROOTSERIAL", record.ParentStableId, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("PCIROOT", record.LocationPathHashes[0], StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void WarningsAndErrorsFlowIntoSnapshot()
+    {
+        var snapshot = new PimaxUsbEnumerationSnapshotCollector(
+            new FakeInventorySource([], ["warning"], ["error"]))
+            .Collect();
+
+        Assert.Equal(["warning"], snapshot.Warnings);
+        Assert.Equal(["error"], snapshot.Errors);
+    }
+
+    [Fact]
+    public void ExistingConnectivitySchemaConstantRemainsUnchanged()
+    {
+        Assert.Equal("pimax-connectivity-v1", PimaxConnectivitySchema.Version);
+        Assert.Equal("pimax-usb-enumeration-v1", PimaxUsbEnumerationSchema.Version);
+    }
+
+    private static PimaxUsbRawDeviceRecord Raw(
+        string instanceId,
+        string? parentInstanceId = null,
+        string? containerId = null,
+        string enumeratorName = "USB",
+        bool present = true,
+        bool connected = true,
+        bool phantom = false,
+        string? deviceClass = "USB",
+        string? friendlyName = "Fake Pimax Device",
+        string? deviceDescription = "Fake Pimax Device",
+        string? manufacturer = "Pimax",
+        string? status = "Started",
+        int? problemCode = null,
+        string[]? hardwareIds = null,
+        string[]? compatibleIds = null,
+        string? vid = "34A4",
+        string? pid = "0012",
+        string[]? locationPaths = null)
+        => new(
+            instanceId,
+            parentInstanceId,
+            containerId,
+            enumeratorName,
+            present,
+            connected,
+            phantom,
+            deviceClass,
+            "{FAKE-CLASS-GUID}",
+            friendlyName,
+            deviceDescription,
+            manufacturer,
+            "fake-service",
+            null,
+            null,
+            null,
+            status,
+            problemCode,
+            problemCode is > 0 ? "Problem" : status,
+            hardwareIds ?? [@"USB\VID_34A4&PID_0012"],
+            compatibleIds ?? [],
+            vid,
+            pid,
+            null,
+            null,
+            "Port_#0001.Hub_#0002",
+            locationPaths ?? [],
+            [],
+            "FakeSource");
+
+    private sealed class FakeInventorySource(
+        PimaxUsbRawDeviceRecord[] devices,
+        string[]? warnings = null,
+        string[]? errors = null) : IPimaxUsbDeviceInventorySource
+    {
+        public PimaxUsbInventoryResult Collect()
+            => new(devices, warnings ?? [], errors ?? []);
+    }
+}