pubsub/tasks/003-redis-adapter-tests.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
redis-adapter-tests	Write tests for Redis event target adapter	completed	core-pubsub-tests	moderate	medium	component	implementation

Description

The Redis event target adapter (event-target-redis.ts) is implemented but has zero tests. The architecture doc lists 7 specific test scenarios. Tests need a running Redis instance or a mock. Since this is a dev dependency, we can use ioredis-mock or start a Redis container in CI. The test strategy needs to handle the Redis dependency.

The architecture specifies these test scenarios:

1. Publish path — dispatchEvent sends to Redis with correct channel and serialized envelope
2. Subscribe path — addEventListener subscribes to Redis, onMessage dispatches to local listeners
3. Unsubscribe — removeEventListener unsubscribes from Redis when no listeners remain for a topic
4. Topic scoping — type:id topics are correctly formed
5. Envelope serialization — full { type, id, payload } round-trips through JSON
6. Multiple listeners — multiple listeners on same topic, single Redis subscribe
7. Error propagation — what happens on connection failure

Note: test 7 (error propagation) is partially blocked by the missing error handling in the current implementation (tracked in task redis-channel-prefix-and-error-handling). The test should exist but may need to be adjusted once error handling is added.

Acceptance Criteria

• test/event-target-redis.test.ts exists and passes
• Test approach for Redis dependency is decided (mock, container, or ioredis-mock)
• Test: dispatchEvent publishes correct channel and serialized envelope
• Test: addEventListener subscribes to Redis and dispatches to local listeners
• Test: removeEventListener unsubscribes from Redis when no listeners remain
• Test: type:id topic scoping works correctly
• Test: EventEnvelope round-trips through JSON serialization
• Test: multiple listeners on same topic result in single Redis subscribe
• Test: custom serializer option works

References

• docs/architecture/event-targets/redis.md
• src/event-target-redis.ts

Notes

Test approach: Manual Redis mock (no external dependencies). The createMockRedis() helper creates a lightweight mock that tracks publish/subscribe/unsubscribe calls and provides simulateMessage() to trigger the message event handler. This avoids needing ioredis-mock or a running Redis instance.

Test 7 (error propagation) is not included because the current implementation lacks error handling — tracked in redis-channel-prefix-and-error-handling task.

Summary

Implemented comprehensive tests for the Redis event target adapter using a manual mock approach (no external dependencies needed).

• Created: test/event-target-redis.test.ts (17 tests across 7 describe blocks)
• Tests: 17, all passing
• Coverage: dispatchEvent/publish path, addEventListener/subscribe path, removeEventListener/unsubscribe path, topic scoping, envelope round-trip serialization, multiple listeners (single Redis subscribe), custom serializer, EventListenerObject support