email-connect/workplans/EMAIL-WP-0005-test-mailbox-harness.md

---
id: EMAIL-WP-0005
type: workplan
title: "Test Mailbox Harness for Automated Test Environments"
domain: infotech
repo: email-connect
status: proposed
owner: claude
topic_slug: custodian
created: "2026-08-14"
updated: "2026-08-14"
---

# EMAIL-WP-0005 - Test Mailbox Harness for Automated Test Environments

## 1. Purpose

Automated test environments need mail accounts for test users so that
end-to-end flows (invitation send, verification, return-path evidence) can be
exercised without a production provider and without hand-crafted fixtures for
every case.

This workplan adds a **test mailbox harness**: a Maildir mailbox source, a
containerized SMTP/IMAP test server, deterministic test-user accounts, and
end-to-end tests that drive `/v1/send` into the harness and scan the resulting
mailboxes back out through the existing scanner.

The harness is test infrastructure. It does not make `email-connect` a mail
provider or an MTA operator, and it must not weaken the evidence discipline:
mail observed in a test server is still provider/MX-level fact, never proof of
delivery, awareness, identity, or authorization.

## 2. User Story

As a developer or CI job, I want to start one container, send invitation and
verification mail through `email-connect` to per-test mailboxes, and then scan
those mailboxes with the normal scanner path, so that I can assert on end-to-end
behavior without a live provider and without network egress.

## 3. In Scope

- A `maildir` mailbox source alongside the existing `fixture` and `imap`
  sources.
- A containerized SMTP + IMAP test server for integration tests.
- Deterministic per-test-user account provisioning and reset.
- End-to-end tests: send through the transactional service, scan through the
  scanner, assert evidence rows.
- A documented strategy for bounce/complaint/deferral realism, which local
  servers cannot generate honestly.
- Documentation and a decision record for the chosen approach.

## 4. Out of Scope

- Operating a production or internet-facing MTA.
- Owning DNS, TLS certificates, rDNS, SPF/DKIM/DMARC, or spam filtering.
- Mailbox write-back actions (the scanner stays read-only; `mark_seen` remains
  rejected).
- A mailbox management UI or user-facing account provisioning.
- Replacing the fixture path as the default test source.
- Integrating s/qmail — see `DECISIONS.md`, "Test mailbox harness: purpose-built
  test server over s/qmail".

## 5. Design Constraints

The harness must respect the existing seams rather than introduce new ones:

```text
mailbox.protocol     fixture | imap | maildir     (src/email_connect/mailbox.py)
SMTP provider        EMAIL_CONNECT_SMTP_HOST/PORT (src/email_connect/transactional.py)
```

Pointing tests at the harness must require configuration only, not code
branching inside the scanner or the transactional application. No test-only
code paths may exist in the production send or scan logic.

The fixture source remains the default for unit tests: deterministic, offline,
no container required. The harness is the *integration* tier.

## 6. Evidence Semantics

Mail retrieved from a test server carries exactly the same evidence ceiling as
mail retrieved from a real mailbox. Specifically, the harness must not be used
to justify any of:

```text
message was delivered to a real inbox
recipient became aware of the message
recipient identity was verified
recipient was authorized
```

A test-server acceptance is `provider_accepted` and nothing more. Tests that
assert stronger claims are defects in the test, not features of the harness.

## 7. Work Packages

## T01 - Maildir mailbox source

```task
id: EMAIL-WP-0005-T01
status: todo
priority: high
```

Tasks:

```text
Add protocol: maildir to config and AppConfig validation
Implement MaildirMailboxSource reading new/ and cur/ per Maildir spec
Derive stable message identity from Maildir filename plus existing dedup keys
Support incremental scans via scan_cursors for maildir sources
Preserve raw_message_ref as a maildir:// reference
Reject mark_seen for maildir the same way IMAP does
Wire the source into source_for_config
Add unit tests over a temporary Maildir tree
```

Acceptance:

```text
The scanner reads a Maildir directory, classifies messages, and produces the
same evidence rows as the equivalent fixture directory, with deduplication and
incremental cursors working across repeated scans.
```

## T02 - Containerized SMTP/IMAP test server

```task
id: EMAIL-WP-0005-T02
status: todo
priority: high
```

Tasks:

```text
Select and pin a test mail server image providing SMTP and IMAP
Add a compose or container definition under a test harness directory
Expose SMTP and IMAP on fixed local ports with non-secret test credentials
Document startup, teardown, and health check
Add a config profile pointing mailbox.protocol imap at the harness
Add a config profile pointing the SMTP provider env vars at the harness
Ensure the harness never binds a routable interface by default
```

Acceptance:

```text
One documented command starts a local mail server; the scanner can complete an
IMAP scan against it and the transactional service can complete a send to it,
using committed non-secret test credentials only.
```

Notes:

```text
Preferred candidate is GreenMail, which serves SMTP and IMAP and creates
accounts on demand. Mailpit is the fallback for send-side-only inspection and
does not exercise the IMAP source. Record the choice in DECISIONS.md.
```

## T03 - Test-user account provisioning and reset

```task
id: EMAIL-WP-0005-T03
status: todo
priority: high
```

Tasks:

```text
Define the test-user address convention and test domain
Provide a helper to create or address per-test mailboxes deterministically
Provide per-test reset so state does not leak between tests
Keep test credentials non-secret and committed, never routed through OpenBao
Document the convention and the reset contract
```

Acceptance:

```text
A test can obtain an isolated mailbox for a named test user, send to it, read
it back, and reset it, with no cross-test interference and no real credentials
involved.
```

Notes:

```text
Test credentials are deliberately non-secret and belong in the repo. Per
.claude/rules/credential-routing.md, OpenBao and warden route are for real
provider material; the harness must not touch them.
```

## T04 - End-to-end send-and-scan integration tests

```task
id: EMAIL-WP-0005-T04
status: todo
priority: high
```

Tasks:

```text
Add an integration test tier that is skipped when the harness is unavailable
Drive /v1/send invitation and verification flows into harness mailboxes
Scan the resulting mailboxes through the normal scanner path
Assert evidence rows, evidence_ceiling, and absence of overclaiming
Cover idempotency and duplicate-request behavior end to end
Cover suppression behavior end to end
Ensure the default unit test run stays offline and container-free
```

Acceptance:

```text
An integration run proves send-to-scan continuity against a live local server,
while the default test run remains offline, deterministic, and unchanged.
```

## T05 - Bounce, complaint, and deferral realism

```task
id: EMAIL-WP-0005-T05
status: todo
priority: medium
```

Tasks:

```text
Document that local servers do not generate realistic DSNs, complaints, or deferrals
Keep crafted .eml fixtures as the deterministic path for those classes
Add a helper to inject fixture messages into a harness mailbox or Maildir
Define an optional staging tier using provider simulator addresses
Document which evidence classes are only reachable in the staging tier
```

Acceptance:

```text
Every evidence class the parser recognizes has a documented, reachable test
path, and the limits of the local harness are stated explicitly rather than
papered over.
```

## T06 - Documentation and decision record

```task
id: EMAIL-WP-0005-T06
status: todo
priority: medium
```

Tasks:

```text
Write a test harness tutorial covering start, send, scan, assert, reset
Extend docs/mailbox-report-tutorial.md with the maildir source
Record the DECISIONS.md entry for the harness approach and the s/qmail rejection
Document the three test tiers: fixture unit, harness integration, provider staging
Document the evidence ceiling that applies to harness-observed mail
```

Acceptance:

```text
A new contributor can start the harness, run the integration tier, and
correctly state what harness-observed mail does and does not prove.
```

## 8. Completion Criteria

This workplan is complete when:

1. `mailbox.protocol: maildir` is supported, tested, and documented.
2. A pinned containerized SMTP/IMAP test server starts from one documented
   command with committed non-secret credentials.
3. Test users get isolated, resettable mailboxes by convention.
4. Integration tests prove send-to-scan continuity while the default test run
   stays offline and container-free.
5. Every recognized evidence class has a documented, reachable test path, with
   local-harness limits stated explicitly.
6. Documentation and the decision record are in place, including the evidence
   ceiling for harness-observed mail.