chore: Test that writing an event keeps its trace context.

src/writeEvents.test.ts

@@ -1,6 +1,7 @@
 import assert from 'node:assert/strict';
 import { afterEach, beforeEach, suite, test } from 'node:test';
 import { Container } from './Container.js';
+import type { Event } from './Event.js';
 import type { EventCandidate } from './EventCandidate.js';
 import { getImageVersionFromDockerfile } from './getImageVersionFromDockerfile.js';
 import { isEventQlQueryTrue } from './isEventQlQueryTrue.js';
@@ -76,6 +77,45 @@ suite('writeEvents', { timeout: 30_000 }, () => {
 		assert.equal(secondWrittenEvent.data.value, 42);
 	});
 
+	test('writes the trace context of an event.', async (): Promise<void> => {
+		const client = container.getClient();
+
+		const traceparent = '00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01';
+		const tracestate = 'rojo=00f067aa0ba902b7';
+
+		const event: EventCandidate = {
+			source: 'https://www.eventsourcingdb.io',
+			subject: '/test',
+			type: 'io.eventsourcingdb.test',
+			data: {
+				value: 42,
+			},
+			traceparent,
+			tracestate,
+		};
+
+		const writtenEvents = await client.writeEvents([event]);
+
+		assert.equal(writtenEvents.length, 1);
+		const [writtenEvent] = writtenEvents;
+		assert.ok(writtenEvent);
+		assert.equal(writtenEvent.traceparent, traceparent);
+		assert.equal(writtenEvent.tracestate, tracestate);
+
+		const eventsRead: Event[] = [];
+		for await (const eventRead of client.readEvents('/test', {
+			recursive: false,
+		})) {
+			eventsRead.push(eventRead);
+		}
+
+		assert.equal(eventsRead.length, 1);
+		const [eventRead] = eventsRead;
+		assert.ok(eventRead);
+		assert.equal(eventRead.traceparent, traceparent);
+		assert.equal(eventRead.tracestate, tracestate);
+	});
+
 	test('supports the isSubjectPristine precondition.', async (): Promise<void> => {
 		const client = container.getClient();