pubsub/tasks/002-core-operators-tests.md

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

id	name	status	depends_on	scope	risk	impact	level
core-operators-tests	Write tests for all stream operators	completed		moderate	low	component	implementation

Description

The operators.ts module exports 13 operators (filter, map, pipe, take, reduce, toArray, batch, dedupe, window, flat, groupBy, chain, join). None have tests. Each operator works with AsyncIterable input; Repeater-returning operators (filter, map) provide backpressure-aware push semantics.

The operators are adapted from graphql-yoga (filter, map, pipe) and added from the async-utility reference (take, reduce, toArray, batch, dedupe, window, flat, groupBy, chain, join).

Acceptance Criteria

• test/operators.test.ts exists and passes
• filter — filters items by predicate; type-narrowing overload works
• filter — async predicate support
• map — transforms items; async mapper support
• pipe — composes 1-5 functions
• pipe — compose with subscribe: pipe(pubsub.subscribe("myEvent", id), filter(...), map(...))
• take — yields first N items, then stops
• reduce — reduces to single value
• toArray — collects all items into array
• batch — groups into arrays of size
• batch — yields remaining items if not a full batch
• dedupe — yields only unique items
• window — sliding window of size items, advancing by step
• flat — flattens AsyncIterable<T[]> into AsyncIterable<T>
• groupBy — groups items by key into Map (terminal operation)
• chain — concatenates multiple async iterables
• join — streaming join between two sources on matching keys

References

• docs/architecture/api-surface.md (Operators section)
• src/operators.ts

Notes

To be filled by implementation agent

Summary

Implemented comprehensive tests for all 13 stream operators.

• Created: test/operators.test.ts (53 tests)
• Tests cover: filter (5 tests including type-narrowing & async), map (3 tests including async), pipe (6 tests including compose with subscribe), take (4), reduce (4), toArray (3), batch (5), dedupe (4), window (5), flat (3), groupBy (3), chain (4), join (4)
• All 53 tests passing, build and lint pass