---
id: core-pubsub-tests
name: Write tests for createPubSub, EventEnvelope, and in-process event target
status: completed
depends_on: []
scope: moderate
risk: low
impact: component
level: implementation
---

## Description

The core `createPubSub` factory, `EventEnvelope` type, and the in-process (default `EventTarget`) path have no tests. These are the foundation of the entire package — every adapter builds on `createPubSub`. Write comprehensive tests that verify the core contract.

The architecture specifies these behaviors:
- `createPubSub()` with no config uses `new EventTarget()` (in-process)
- `createPubSub({ eventTarget })` uses a custom event target
- `publish(type, id, payload)` dispatches a `CustomEvent` with type `"type:id"` and `detail` as `EventEnvelope`
- `subscribe(type, id)` returns a `Repeater<EventEnvelope>` (async iterable)
- `publish` throws on event types starting with `__` (reserved for adapter control)
- Topic scoping uses the `type:id` convention
- `subscribe` cleanup: breaking out of the `for await` loop removes the listener

## Acceptance Criteria

- [ ] `test/create_pubsub.test.ts` exists and passes
- [ ] Test: `publish` dispatches event with correct `type:id` topic
- [ ] Test: `publish` throws on `__`-prefixed event types
- [ ] Test: `subscribe` returns async iterable that yields `EventEnvelope` objects
- [ ] Test: `subscribe` envelope has correct `type`, `id`, `payload` fields
- [ ] Test: subscriber receives events only for the subscribed topic (type:id matching)
- [ ] Test: multiple subscribers on the same topic all receive events
- [ ] Test: subscriber cleanup — breaking out of `for await` loop removes the listener
- [ ] Test: `createPubSub` with custom `eventTarget` dispatches to that target
- [ ] Test: `createPubSub` without `eventTarget` uses `new EventTarget()` (in-process)

## References

- docs/architecture/api-surface.md
- src/create_pubsub.ts
- src/types.ts

## Notes

Used subscribe-based testing approach since `createPubSub` doesn't expose the internal `target`. Custom eventTarget tests use `vi.spyOn` on the provided target's `dispatchEvent` method.

## Summary

Implemented comprehensive tests for createPubSub, EventEnvelope, and in-process event target.
- Created: test/create_pubsub.test.ts
- Tests: 11, all passing
- Coverage: publish dispatches correct type:id topic, publish throws on __-prefixed types, subscribe yields EventEnvelope objects, envelope has correct type/id/payload, topic scoping (type:id matching), multiple subscribers receive events, subscriber cleanup on break, custom eventTarget dispatches to provided target, default in-process EventTarget works