How do I mock the Slack Web API locally?

Install stunt, add a one-service block to stunt.yaml (adapter: embedded:slack-style), and run stunt up. You get a local, stateful stand-in for Slack Web API 1.0 — 7 routes over rest — with no remote account, no network, and no bills.

Is the Slack Web API mock data synthetic?

Yes — entirely. The adapter returns generated data only; stunt's adapter lint rejects real-looking secrets and PII at build time. It simulates the shape and behavior of Slack Web API (routes, status codes, pagination, webhooks), never real records.

← all adapters

slack-style

simulates Slack Web API 1.0

restadapter v0.1.07 routes

verification

SDKverified with slack-node 7.19.0 (floor)· surface 7 · not implemented 6 · differs 2

use it

# add to stunt.yaml
services:
  slack:
    adapter: embedded:slack-style

# then
$ stunt up

The embedded: source extracts this adapter from the binary — no git clone, fully offline.

how to mock the Slack Web API locally

Install stunt, paste the service block above into stunt.yaml, run stunt up — then point your client at localhost instead of Slack Web API. It works offline, keeps state across requests and restarts, and every response is synthetic: the route shapes, status codes, pagination, and webhook delivery follow the real Slack Web API 1.0 surface — the data is fake, the behavior is real.

backing stores

channelsmessages

api surface (7)

generated from the adapter manifest — exactly what boots, nothing more · covers 2% of the real API's 272 routes (derived from sdk slack-node @ 7.19.0 (floor))

7 routes

POST/api/auth.test

POST/api/chat.postMessage

POST/api/conversations.create

/api/conversations.list

/api/conversations.history

POST/api/reactions.add

POST/api/apps.events.url

SDK-verified behaviors (4)

✓auth.test validates the seeded bearer token
✓conversations.create + list round-trip
✓chat.postMessage lands in conversations.history
✓reactions.add on the posted message

Not implemented (6)

Only 7 Web API methods; no chat.update, chat.delete, or chat.scheduleMessage
No conversations.members, join, leave, open, or rename; no users.list/users.info
No reactions.remove or reactions.list
No message threads: conversations.replies and chat.getPermalink absent
No files (files.upload/info/list), search, views, or dialogs surfaces
Only message, channel_created, reaction_added events; no app_mention or team_join

Differs from the real API (2)

apps.events.url config endpoint is simulator-only; real Slack sets it in the app dashboard
Events deliveries wrap Slack event_callback payloads in an extra stunt envelope

full scorecard →

want more of the Slack Web API surface? adapters are YAML + Starlark — the authoring guide covers adding routes, fixtures, and state machines. Open an issue for anything big first, or just file a PR — merged routes ship in the next release.