# Testing prompts

> Drive ask() and resolvePrompts() with a scripted reader and writer — no PTY, no fake stdin — and assert both the answers and exactly what was written.

Source: https://caique.interlace.tools/docs/recipes/testing-prompts

Nothing above `caique/terminal` touches a stream: `ask()` takes a reader of lines and a writer
of text. A test hands it both and asserts the conversation.

```js title="prompt-check.mjs"
import assert from 'node:assert/strict';

import { ask } from 'caique/ask';

function conversation(answers) {
  const lines = [...answers];
  let written = '';
  return {
    io: { reader: { line: async () => lines.shift() }, writer: { write: (text) => void (written += text) } },
    written: () => written,
  };
}

const port = conversation(['eighty', '80']);
const answer = await ask({ kind: 'text', message: 'Port?', validate: (v) => (/^\d+$/u.test(v) ? undefined : 'a port is a number') }, port.io);
assert.deepEqual(answer, { ok: true, value: '80' });
assert.equal(port.written(), 'Port?   a port is a number\nPort? ');

const closed = conversation([]);
assert.deepEqual(await ask({ kind: 'confirm', message: 'Continue?' }, closed.io), { ok: false, reason: 'cancelled' });

console.log('ok');
```

```text title="node prompt-check.mjs"
ok
```

The second case is the one that matters most: a stream that ends — `Ctrl-D`, a closed pipe, an
empty script — is a cancellation, never an empty answer. `decide()` needs no stream at all; it
is a pure function of a literal runtime ([Never hangs](/docs/guides/never-hangs)).