nodejs/test/parallel/test-stream-duplex.js

// Copyright Joyent, Inc. and other Node contributors.
//
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// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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'use strict';

const common = require('../common');
const assert = require('assert');
const Duplex = require('stream').Duplex;

const stream = new Duplex({ objectMode: true });

assert(Duplex() instanceof Duplex);
assert(stream._readableState.objectMode);
assert(stream._writableState.objectMode);

let written;
let read;

stream._write = (obj, _, cb) => {
  written = obj;
  cb();
};

stream._read = common.noop;

stream.on('data', (obj) => {
  read = obj;
});

stream.push({ val: 1 });
stream.end({ val: 2 });

process.on('exit', () => {
  assert.strictEqual(read.val, 1);
  assert.strictEqual(written.val, 2);
});