node/test/parallel/test-crypto-lazy-transform-writable.js

'use strict';

const common = require('../common');
if (!common.hasCrypto)
  common.skip('missing crypto');

const assert = require('assert');
const crypto = require('crypto');
const Stream = require('stream');

const hasher1 = crypto.createHash('sha256');
const hasher2 = crypto.createHash('sha256');

// Calculate the expected result.
hasher1.write(Buffer.from('hello world'));
hasher1.end();

const expected = hasher1.read().toString('hex');

class OldStream extends Stream {
  constructor() {
    super();
    this.readable = true;
  }
}

const stream = new OldStream();

stream.pipe(hasher2).on('finish', common.mustCall(function() {
  const hash = hasher2.read().toString('hex');
  assert.strictEqual(hash, expected);
}));

stream.emit('data', Buffer.from('hello'));
stream.emit('data', Buffer.from(' world'));
stream.emit('end');