# `fake-smtp-client.ts`

## Purpose

Deterministic test double for `SmtpClientLike`. Tests queue scripted
responses, invoke the wrapped `SmtpTransport`, and inspect the captured
calls — without `vi.mock`, without a real SMTP server, and without
monkey-patching globals. Shipping the fake from the package itself means
downstream consumers can test their integration against the same exact
shape `SmtpTransport` produces, without re-implementing the protocol fake.

## Features

- `push(response)` queues a scripted outcome (`info` for success, `reject`
  for failure).
- `calls` captures every `sendMail` invocation in FIFO order so
  assertions can target individual recipients / headers / attachments.
- `scheduleVerify(true | false | Error)` programs the next `verify()` call.
- `verifyCalls` and `closeCalls` track lifecycle so tests can assert
  cleanup behaviour.

## Usage: Basic

```ts
import { FakeSmtpClient } from "@suaveplan/emailer/fakes/fake-smtp-client";
import { SmtpTransport } from "@suaveplan/emailer/transports/smtp";

const adapter = new FakeSmtpClient();
adapter.push({ info: { messageId: "<abc@host>" } });

const transport = new SmtpTransport();
await transport.initialize({ client: adapter });
const r = await transport.send({ to: "u@x.y", subject: "hi", text: "hi" });
```

## Usage: Advanced

```ts
import { FakeSmtpClient } from "@suaveplan/emailer/fakes/fake-smtp-client";

const adapter = new FakeSmtpClient();
adapter.push({ reject: new Error("connection refused") });
adapter.push({ info: { messageId: "<1@h>", accepted: ["a@b.c"] } });
adapter.scheduleVerify(true);

// First send fails, second succeeds, verify returns true.
```

## API Reference

- `class FakeSmtpClient implements SmtpClientLike`
- `interface FakeSmtpResponse { info?, reject? }`
- `interface FakeSmtpCall { payload: SmtpSendPayload }`

## Implementation Notes

- The fake is intentionally minimal — it carries no SMTP state, no auth,
  no connection pool. The point is that `SmtpTransport` only ever calls
  three methods (`sendMail`, `verify`, `close`), and the fake reproduces
  exactly those three semantics with FIFO scripting.
- `scheduleVerify(Error)` is single-use — after the next `verify` throws,
  the reject queue clears. Subsequent calls return the most-recently
  scheduled boolean (default `true`).
- `closeCalls` increments on every `close`, allowing tests to assert
  idempotent close behaviour without inspecting private state.