test: read an ErrorResponse off the broker; every answer has its own messageId

Step 2 replaced uuid by crypto.randomUUID() at three call sites (AlexaStatusMessage, AlexaErrorResponse,
Device.sendSceneResponse) and only the first was asserted, in the ES module test. With the messageId dropped or set
to a constant in the other two, the suite still passed 22/22, and no test read an ErrorResponse at all.

New: an ErrorResponse compared whole against the documented shape (header, endpoint, payload, no context), and one
test that sends two directives each to a light, an unreachable light and a scene and requires six different
version 4 UUIDs. The Response, StateReport, scene and change report tests check the messageId too; the pattern
lives in the harness.

Checked in a scratch copy: a missing or constant messageId at each of the three sites now fails the suite (the
missing one in AlexaStatusMessage does not compile). No change to src/ or dist/. npm test: 24 pass in 5.5 s.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

test/change-report.test.js

@@ -4,7 +4,7 @@
 const { test } = require("node:test");
 const assert = require("node:assert/strict");
 const { Alex2MQTT, AlexaInterfaceType, DisplayCategory, PowerController } = require("alex2node");
-const { setup, until } = require("./helpers/harness.js");
+const { setup, until, UUID_V4 } = require("./helpers/harness.js");
 
 test("a change report carries the changed properties in payload.change and the rest in context", async () => {
   const { alexa, bridge } = await setup(Alex2MQTT, "root");
@@ -22,6 +22,7 @@ test("a change report carries the changed properties in payload.change and the r
   await until(() => alexa.on("root/changeReport").length === 1, 3000, "change report");
   const [report] = alexa.on("root/changeReport");
   assert.equal(report.event.header.name, "ChangeReport");
+  assert.match(report.event.header.messageId, UUID_V4);
   assert.equal(report.event.endpoint.endpointId, "5020AA");
   assert.equal(report.event.payload.change.cause.type, "PHYSICAL_INTERACTION");
   assert.deepEqual(report.event.payload.change.properties.map((p) => [p.name, p.value]), [["powerState", "OFF"]]);

test/directives.test.js

@@ -4,9 +4,9 @@
 const { test } = require("node:test");
 const assert = require("node:assert/strict");
 const {
-  Alex2MQTT, AlexaInterfaceType, DisplayCategory, PowerController, EndpointHealth, TemperatureSensorScale,
+  Alex2MQTT, AlexaErrorType, AlexaInterfaceType, DisplayCategory, PowerController, EndpointHealth, TemperatureSensorScale,
 } = require("alex2node");
-const { setup, directive, until } = require("./helpers/harness.js");
+const { setup, directive, until, UUID_V4 } = require("./helpers/harness.js");
 
 // A light that answers every directive with its new power state and ReportState with "off at 0 %".
 function diningRoomLight(bridge) {
@@ -29,6 +29,28 @@ function diningRoomLight(bridge) {
   return lamp;
 }
 
+// A light that is not there: every directive is answered with ENDPOINT_UNREACHABLE.
+function unpluggedLight(bridge) {
+  const lamp = bridge.registerDevice("Garage Light", "5020AB", DisplayCategory.LIGHT);
+  lamp.addCapability(AlexaInterfaceType.POWER_CONTROLLER);
+  lamp.on("Event", (request) => {
+    const error = lamp.getErrorMessage(request.header.correlationToken);
+    error.setErrorMessage(AlexaErrorType.ENDPOINT_UNREACHABLE, "the light is unplugged");
+    error.send();
+  });
+  return lamp;
+}
+
+// A scene that answers Activate and Deactivate with the matching event.
+function eveningScene(bridge) {
+  const scene = bridge.registerDevice("Evening", "scene-1", DisplayCategory.SCENE_TRIGGER);
+  scene.addCapability(AlexaInterfaceType.SCENE_CONTROLLER);
+  scene.on("Event", (request) => {
+    scene.sendSceneResponse(request.header.correlationToken, request.header.name === "Activate");
+  });
+  return scene;
+}
+
 test("a directive reaches the \"Event\" listener and is answered with a Response carrying its correlationToken", async () => {
   const { alexa, bridge } = await setup(Alex2MQTT, "root");
   const dispatched = [];
@@ -40,6 +62,7 @@ test("a directive reaches the \"Event\" listener and is answered with a Response
   const [response] = alexa.on("root/5020AA/alexaResponce");
   assert.equal(response.event.header.name, "Response");
   assert.equal(response.event.header.correlationToken, "ct1");
+  assert.match(response.event.header.messageId, UUID_V4);
   assert.equal(response.context.properties.find((p) => p.name === "powerState").value, "ON");
   assert.deepEqual(dispatched, [{ endpointId: "5020AA", namespace: "Alexa.PowerController", name: "TurnOn" }]);
 });
@@ -53,26 +76,65 @@ test("ReportState reaches the \"ReportState\" listener and is answered with a St
   const [report] = alexa.on("root/5020AA/alexaResponce");
   assert.equal(report.event.header.name, "StateReport");
   assert.equal(report.event.header.correlationToken, "ct2");
+  assert.match(report.event.header.messageId, UUID_V4);
   assert.deepEqual(report.context.properties.map((p) => [p.name, p.value]), [["powerState", "OFF"], ["brightness", 0]]);
 });
 
+test("getErrorMessage: the directive is answered with an ErrorResponse, the error type and message as its payload", async () => {
+  const { alexa, bridge } = await setup(Alex2MQTT, "root");
+  unpluggedLight(bridge);
+
+  alexa.send("root", directive("Alexa.PowerController", "TurnOn", "5020AB", "ct4"));
+  await until(() => alexa.on("root/5020AB/alexaResponce").length === 1, 3000, "error response");
+  const [answer] = alexa.on("root/5020AB/alexaResponce");
+  const { messageId, ...header } = answer.event.header;
+  assert.match(messageId, UUID_V4);
+  // The event alone, without a context (Alexa.ErrorResponse, "Synchronous error response")
+  assert.deepEqual({ ...answer, event: { ...answer.event, header } }, {
+    event: {
+      header: { namespace: "Alexa", name: "ErrorResponse", correlationToken: "ct4", payloadVersion: "3" },
+      endpoint: { endpointId: "5020AB" },
+      payload: { type: "ENDPOINT_UNREACHABLE", message: "the light is unplugged" },
+    },
+  });
+});
+
 test("SceneController: Activate is answered with ActivationStarted", async () => {
   const { alexa, bridge } = await setup(Alex2MQTT, "root");
-  const scene = bridge.registerDevice("Evening", "scene-1", DisplayCategory.SCENE_TRIGGER);
-  scene.addCapability(AlexaInterfaceType.SCENE_CONTROLLER);
-  scene.on("Event", (request) => {
-    scene.sendSceneResponse(request.header.correlationToken, request.header.name === "Activate");
-  });
+  eveningScene(bridge);
 
   alexa.send("root", directive("Alexa.SceneController", "Activate", "scene-1", "ct3"));
   await until(() => alexa.on("root/scene-1/alexaResponce").length === 1, 3000, "scene response");
   const [started] = alexa.on("root/scene-1/alexaResponce");
   assert.equal(started.event.header.namespace, "Alexa.SceneController");
   assert.equal(started.event.header.name, "ActivationStarted");
+  assert.match(started.event.header.messageId, UUID_V4);
   assert.equal(started.event.payload.cause.type, "VOICE_INTERACTION");
   assert.ok(started.event.payload.timestamp);
 });
 
+test("no two answers share a messageId: Response, ErrorResponse and the scene events each get a new one", async () => {
+  const { alexa, bridge } = await setup(Alex2MQTT, "root");
+  diningRoomLight(bridge);
+  unpluggedLight(bridge);
+  eveningScene(bridge);
+  const answers = () => alexa.got.filter((m) => m.topic.endsWith("/alexaResponce")).map((m) => m.payload.event.header);
+
+  for (const token of ["first", "second"]) {
+    alexa.send("root", directive("Alexa.PowerController", "TurnOn", "5020AA", token));
+    alexa.send("root", directive("Alexa.PowerController", "TurnOn", "5020AB", token));
+    alexa.send("root", directive("Alexa.SceneController", "Activate", "scene-1", token));
+  }
+  await until(() => answers().length === 6, 3000, "six answers");
+  assert.deepEqual(
+    answers().map((header) => header.name).sort(),
+    ["ActivationStarted", "ActivationStarted", "ErrorResponse", "ErrorResponse", "Response", "Response"]
+  );
+  const ids = answers().map((header) => header.messageId);
+  for (const id of ids) assert.match(id, UUID_V4);
+  assert.equal(new Set(ids).size, 6, `a messageId is used twice: ${ids.join(" ")}`);
+});
+
 test("the temperature helpers convert Fahrenheit to Celsius (as 1.4.0 did)", async () => {
   const { bridge } = await setup(Alex2MQTT, "root");
   const lamp = diningRoomLight(bridge);

test/helpers/harness.js

@@ -22,6 +22,10 @@ function cleanup(fn) {
 
 const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
 
+// What crypto.randomUUID() returns. Alexa wants a new messageId in every response and event and recommends a
+// version 4 UUID (Message guide, "Header object").
+const UUID_V4 = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/;
+
 /** Poll fn every 15 ms until it returns something truthy. Throws "timeout waiting for <what>" after ms. */
 async function until(fn, ms = 3000, what = "condition") {
   const start = Date.now();
@@ -102,4 +106,4 @@ async function setup(Alex2MQTT, root, options = {}) {
   return { url, alexa, bridge };
 }
 
-module.exports = { broker, watcher, directive, connected, setup, until, sleep, cleanup };
+module.exports = { broker, watcher, directive, connected, setup, until, sleep, cleanup, UUID_V4 };

test/packaging.test.mjs

@@ -5,7 +5,7 @@ import assert from "node:assert/strict";
 import { Alex2MQTT, AlexaInterfaceType, DisplayCategory, EndpointHealth, PowerController } from "alex2node";
 import harness from "./helpers/harness.js";
 
-const { setup, directive, until } = harness;
+const { setup, directive, until, UUID_V4 } = harness;
 
 test("import { Alex2MQTT } from \"alex2node\": discovery, a directive and a change report on the ES module build", async () => {
   const { alexa, bridge } = await setup(Alex2MQTT, "root");
@@ -30,8 +30,7 @@ test("import { Alex2MQTT } from \"alex2node\": discovery, a directive and a chan
   const [response] = alexa.on("root/lamp-1/alexaResponce");
   assert.equal(response.event.header.name, "Response");
   assert.equal(response.event.header.correlationToken, "ct1");
-  // crypto.randomUUID() writes the messageId: a version 4 UUID, as uuid's v4() did
-  assert.match(response.event.header.messageId, /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/);
+  assert.match(response.event.header.messageId, UUID_V4);
 
   assert.equal(await lamp.getChangeReport().addPowerControllerProp(PowerController.OFF).send(), "root/changeReport");
   await until(() => alexa.on("root/changeReport").length === 1, 3000, "change report");