1 files changed, 79 insertions, 0 deletions
diff --git a/test/timesync.test.ts b/test/timesync.test.ts
new file mode 100644
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--- /dev/null
+++ b/test/timesync.test.ts
@@ -0,0 +1,79 @@
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+import { describe, expect, it } from "vitest";
+import type { TimeSyncSummary } from "../src/inspection.js";
+import { compareDeviceClock } from "../src/sync.js";
+import { capabilitiesFromTimeSync, planTimeSync } from "../src/timesync.js";
+
+/**
+ * Tests driven by the captured `inspect --json` output of the real device
+ * (IKEA ALPSTUGA air quality monitor, firmware 1.0.26), per the plan: the
+ * sync behavior is derived from inspected capabilities, not assumptions.
+ */
+
+const fixture = JSON.parse(readFileSync(join(__dirname, "fixtures", "alpstuga-inspect.json"), "utf8")) as {
+  basicInformation: { vendorName: string; productName: string };
+  timeSynchronization: TimeSyncSummary;
+};
+
+describe("alpstuga fixture", () => {
+  it("is the expected device", () => {
+    expect(fixture.basicInformation.vendorName).toBe("IKEA of Sweden");
+    expect(fixture.timeSynchronization).not.toBeNull();
+  });
+
+  it("derives capabilities from the inspection", () => {
+    const capabilities = capabilitiesFromTimeSync(fixture.timeSynchronization);
+    expect(capabilities).toEqual({
+      timeZoneFeature: true,
+      supportsSetUtcTime: true,
+      supportsSetTimeZone: true,
+      supportsSetDstOffset: true,
+      timeZoneListMaxSize: 2,
+      dstOffsetListMaxSize: 2,
+    });
+  });
+
+  it("plans UTC + time zone + a 2-entry DST list for this device", () => {
+    const capabilities = capabilitiesFromTimeSync(fixture.timeSynchronization);
+    const plan = planTimeSync(capabilities, "America/Chicago", new Date("2026-07-26T00:00:00Z"));
+    expect(plan.setUtcTime).toBe(true);
+    expect(plan.timeZone).toEqual([
+      { offset: -21600, validAt: 946_684_800_000_000n, name: "America/Chicago" },
+    ]);
+    expect(plan.dstOffsets).toHaveLength(2);
+    expect(plan.dstOffsets![0]!.offset).toBe(3600);
+    expect(plan.dstOffsets![1]!.offset).toBe(0);
+  });
+
+  it("reads the fixture's utcTime as healthy Unix-epoch microseconds", () => {
+    // matter.js's TlvEpochUs decodes wire values to Unix-epoch microseconds,
+    // so the fixture's utcTime (read at commissioning, 2026-07-27T00:18:15Z
+    // wall clock) compares cleanly against that instant with no epoch shift.
+    const attribute = fixture.timeSynchronization.attributes.find(a => a.name === "utcTime");
+    const deviceMicros = BigInt(attribute!.value as string);
+    const captureInstant = BigInt(Date.parse("2026-07-27T00:18:20Z")) * 1_000n;
+    const comparison = compareDeviceClock(deviceMicros, captureInstant);
+    expect(comparison.epochShifted).toBe(false);
+    expect(comparison.deviceTime).toBe("2026-07-27T00:18:15.000Z");
+    const effective = comparison.effectiveDeltaMicroseconds!;
+    const magnitude = effective < 0n ? -effective : effective;
+    expect(magnitude < 60n * 1_000_000n).toBe(true);
+  });
+
+  it("degrades to UTC-only when the TimeZone feature is absent", () => {
+    const utcOnly: TimeSyncSummary = {
+      ...fixture.timeSynchronization,
+      supportedFeatures: { ...fixture.timeSynchronization.supportedFeatures, timeZone: false },
+      supportedCommands: {
+        ...fixture.timeSynchronization.supportedCommands,
+        setTimeZone: false,
+        setDstOffset: false,
+      },
+    };
+    const plan = planTimeSync(capabilitiesFromTimeSync(utcOnly), "America/Chicago");
+    expect(plan.setUtcTime).toBe(true);
+    expect(plan.timeZone).toBeNull();
+    expect(plan.dstOffsets).toBeNull();
+  });
+});