writable-stream-pipe-spec.ts

import { empty, of, sequenceEqual } from 'ix/asynciterable';
import { map } from 'ix/asynciterable/operators';
import { PassThrough } from 'stream';

(() => {
  if (process.env.TEST_NODE_STREAMS !== 'true') {
    return test('not testing node streams because process.env.TEST_NODE_STREAMS !== "true"', () => {
      /**/
    });
  }

  const through = () => {
    return new PassThrough({
      objectMode: true,
      readableObjectMode: true,
      writableObjectMode: true
    });
  };

  test('AsyncIterable#pipe writable-stream single element', async () => {
    const source = of({ name: 'Frank', custId: 98088 });
    const expected = of('Frank');

    expect(
      await sequenceEqual(expected, source.pipe(through()).pipe(map(x => x.name)))
    ).toBeTruthy();
  });

  test('AsyncIterable#pipe writable-stream maps property', async () => {
    const source = of<any>(
      { name: 'Frank', custId: 98088 },
      { name: 'Bob', custId: 29099 },
      { name: 'Chris', custId: 39033 },
      { name: null, custId: 30349 },
      { name: 'Frank', custId: 39030 }
    );
    const expected = of('Frank', 'Bob', 'Chris', null, 'Frank');

    expect(
      await sequenceEqual(expected, source.pipe(through()).pipe(map(x => x.name)))
    ).toBeTruthy();
  });

  test('AsyncIterable#pipe writable-stream empty', async () => {
    expect(
      await sequenceEqual(empty<number>(), empty<string>().pipe(map((s, i) => s.length + i)))
    ).toBeTruthy();
  });

  test('AsyncIterable#pipe writable-stream map property using index', async () => {
    const source = of(
      { name: 'Frank', custId: 98088 },
      { name: 'Bob', custId: 29099 },
      { name: 'Chris', custId: 39033 }
    );
    const expected = of('Frank', null, null);

    expect(
      await sequenceEqual(
        expected,
        source.pipe(through()).pipe(map((x, i) => (i === 0 ? x.name : null)))
      )
    ).toBeTruthy();
  });

  test('AsyncIterable#pipe writable-stream map property using index on last', async () => {
    const source = of(
      { name: 'Frank', custId: 98088 },
      { name: 'Bob', custId: 29099 },
      { name: 'Chris', custId: 39033 },
      { name: 'Bill', custId: 30349 },
      { name: 'Frank', custId: 39030 }
    );
    const expected = of(null, null, null, null, 'Frank');

    expect(
      await sequenceEqual(
        expected,
        source.pipe(through()).pipe(map((x, i) => (i === 4 ? x.name : null)))
      )
    ).toBeTruthy();
  });

  test('AsyncIterable#pipe writable-stream execution is deferred', async () => {
    let fnCalled = false;
    const source = of(() => {
      fnCalled = true;
      return 1;
    });

    source.pipe(through()).pipe(map(x => x()));

    expect(fnCalled).toBeFalsy();
  });
})();