How do I mock the Gmail API locally?

Install stunt, add a one-service block to stunt.yaml (adapter: embedded:gmail-style), and run stunt up. You get a local, stateful stand-in for Gmail API v1 — 16 routes over rest — with no remote account, no network, and no bills.

Is the Gmail 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 Gmail API (routes, status codes, pagination, webhooks), never real records.

← all adapters

gmail-style

simulates Gmail API v1

restadapter v0.1.016 routes

verification

SDKverified with google-api-go-client v0.293.0· surface 16 · not implemented 6 · differs 3

use it

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

# then
$ stunt up

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

how to mock the Gmail API locally

Install stunt, paste the service block above into stunt.yaml, run stunt up — then point your client at localhost instead of Gmail 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 Gmail API v1 surface — the data is fake, the behavior is real.

backing stores

messageslabelsdrafts

api surface (16)

generated from the adapter manifest — exactly what boots, nothing more · covers 20% of the real API's 79 routes (derived from sdk google-api-go-client @ v0.293.0)

16 routes

GET/gmail/v1/users/{userId}/labels

POST/gmail/v1/users/{userId}/labels

DELETE/gmail/v1/users/{userId}/labels/{id}

POST/gmail/v1/users/{userId}/messages/send

GET/gmail/v1/users/{userId}/messages

POST/gmail/v1/users/{userId}/messages

POST/gmail/v1/users/{userId}/messages/batchModify

POST/gmail/v1/users/{userId}/messages/{messageId}/trash

POST/gmail/v1/users/{userId}/messages/{messageId}/modify

GET/gmail/v1/users/{userId}/messages/{messageId}/attachments/{attachmentId}

GET/gmail/v1/users/{userId}/messages/{messageId}

DELETE/gmail/v1/users/{userId}/messages/{messageId}

GET/gmail/v1/users/{userId}/drafts

POST/gmail/v1/users/{userId}/drafts

DELETE/gmail/v1/users/{userId}/drafts/{id}

GET/gmail/v1/users/{userId}/threads/{threadId}

SDK-verified behaviors (9)

✓Labels.List returns seeded system labels
✓Labels.Create + Labels.List round-trip
✓Messages.Send raw rfc822 -> id + threadId
✓Messages.Get parses the sent raw message into payload headers
✓Messages.List includes sent messages
✓Messages.List MaxResults + PageToken walk pages
✓Messages.Modify AddLabelIds applies
✓Messages.Get Format=metadata returns headers without body
✓Messages.Delete then Get -> googleapi 404

Not implemented (6)

No Gmail search operators (from:, to:, after:, has:attachment) in q
No threads.list, history.list, or watch/stop push endpoints
No drafts send/update/get or threads modify/trash endpoints
No messages.import, untrash, or batchDelete endpoints
No labels get/patch or users.getProfile endpoints
No settings surface: filters, sendAs, forwardingAddresses, vacation

Differs from the real API (3)

q is substring match on snippet + Subject header only
Omitted/0 maxResults returns everything; real API defaults to 100
Label create is idempotent on existing name; real Gmail returns 409

full scorecard →

want more of the Gmail 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.