async-lazystream/test/pipe_test.js

Open Node Streams on demand with async support (original code from https://github.com/jpommerening/node-lazystream)

const stream = require('../lib/lazystream');
const helper = require('./helper');

exports.pipe = {
  readwrite: function(test) {
    const expected = ['line1\n', 'line2\n'];
    const actual = [];
    let readableInstantiated = false;
    let writableInstantiated = false;

    test.expect(3);

    const readable = new stream.Readable(function() {
      readableInstantiated = true;
      return new helper.DummyReadable([].concat(expected));
    });

    const writable = new stream.Writable(function() {
      writableInstantiated = true;
      return new helper.DummyWritable(actual);
    });

    test.equal(readableInstantiated, false, 'DummyReadable should only be instantiated when it is needed');
    test.equal(writableInstantiated, false, 'DummyWritable should only be instantiated when it is needed');

    writable.on('end', function() {
      test.equal(actual.join(''), expected.join(''), 'Piping on demand streams should keep data intact');
      test.done();
    });

    readable.pipe(writable);
  },

  async_readwrite: function(test) {
    const expected = ['line1\n', 'line2\n'];
    const actual = [];
    let readableInstantiated = false;
    let writableInstantiated = false;

    test.expect(3);

    const readable = new stream.Readable(function() {
      return new Promise((resolve) => {
        setTimeout(() => {
          readableInstantiated = true;
          resolve(new helper.DummyReadable([].concat(expected)));
        }, 10);
      });
    });

    const writable = new stream.Writable(function() {
      return new Promise((resolve) => {
        setTimeout(() => {
          writableInstantiated = true;
          resolve(new helper.DummyWritable(actual));
        }, 10);
      });
    });

    test.equal(readableInstantiated, false, 'DummyReadable should only be instantiated when it is needed');
    test.equal(writableInstantiated, false, 'DummyWritable should only be instantiated when it is needed');

    writable.on('end', function() {
      test.equal(actual.join(''), expected.join(''), 'Piping on demand streams should keep data intact');
      test.done();
    });

    readable.pipe(writable);
  },
};