testland/graphql-subscription-test-author

Authors GraphQL subscription resolver test suites over graphql-ws (WebSocket) and graphql-sse (Server-Sent Events) transports: subscribe to event streams via the async-iterator API, assert emitted data shape and sequence, verify connection lifecycle and protocol close codes, and validate auth-on-connect (connectionParams / authenticate callback) plus resolver-level pubsub trigger logic. Use for real-time subscription operations; not for queries or mutations - for those use apollo-server-tests, graphql-yoga-tests, or mercurius-tests.

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Resolver, filter, and error tests

Name: testland/graphql-subscription-test-author
Rating: 75.2 (1 reviews)
Author: testland

Isolate the resolver's pubsub wiring from the transport stack, then assert the filter predicate and error propagation.

Resolver-level pubsub test

Isolate the resolver's pubsub wiring without a full transport stack using the graphql subscribe function directly:

import { subscribe, parse } from 'graphql';
import { schema, pubsub } from './schema';

it('resolver emits events published to the channel', async () => {
  const result = await subscribe({
    schema,
    document: parse('subscription { messageAdded { id text } }'),
  });

  if ('errors' in result) throw new Error('Subscription failed');

  // Publish after subscribing
  pubsub.publish('MESSAGE_ADDED', { messageAdded: { id: '1', text: 'hello' } });

  const { value } = await result.next();
  expect(value.data).toEqual({ messageAdded: { id: '1', text: 'hello' } });

  await result.return?.(); // clean up iterator
});

This tests the resolver in isolation - no WebSocket server, no client library. Pair with transport-layer tests for full coverage.

Event-sequence and filter tests

it('only emits events that pass the filter predicate', async () => {
  const sub = client.iterate({
    query: 'subscription Messages($channel: String!) { messageAdded(channel: $channel) { text } }',
    variables: { channel: 'team-a' },
  });

  pubsub.publish('MESSAGE_ADDED', { channel: 'team-b', messageAdded: { text: 'wrong' } });
  pubsub.publish('MESSAGE_ADDED', { channel: 'team-a', messageAdded: { text: 'right' } });

  const { value } = await sub.next();
  expect(value.data?.messageAdded?.text).toBe('right');
  await sub.return?.();
});

Error propagation tests

Per the-guild.dev/graphql/sse/recipes, resolver errors during a subscription should surface via the iterator, not crash the server:

it('surfaces resolver errors as GraphQL errors, not exceptions', async () => {
  const result = await subscribe({
    schema: errorSchema, // schema whose subscription resolver throws
    document: parse('subscription { failingFeed }'),
  });

  if ('errors' in result) throw new Error('Subscribe itself failed');

  const { value } = await result.next();
  expect(value.errors).toBeDefined();
  expect(value.errors?.[0].message).toMatch(/expected error/i);
});